Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Mains fuse blew in the middle of normal use.
No mention of PbF anywhere but it is. Unlikely the problem though. Seems bad
thermal design as audio-out vaned heatsink has cooling air through it but
the non-vaned SMPS one does not have, as that intended? air will go through
the path of least resistance over the uncluttered preamp . I can see a
baffle going in here to direct air over this plain block heatsink. Anyone
experience of these little amps?
Both SMPS powerFETs s/c all round. Each has a discoloured patch on the
mounting-plate where the die overlies. No burning/blow-holes of these
powerFET encapsulations or 10R SMD gate droppers or anything else found
suspect from cold testing/close inspection, nor suspect looking PbF. The
SMPS supervisor IC ident is ground off and a schematic for a similar amp
has no ident. I could find details of any 8 pin 0.1 inch pitch package with
push/pull drive in 1991 DATA linear colated listing- any suggestions for
this sort of search?
p1 supply low side
p3 probably Enable
p4 Vcc
p5 and p7 hi/lo outputs
p6 mid connection to both output powerFET
Does not seem to be any thermal shutdown for the SMPS section


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy


"N_Cook" wrote in message
...
Mains fuse blew in the middle of normal use.
No mention of PbF anywhere but it is. Unlikely the problem though. Seems
bad
thermal design as audio-out vaned heatsink has cooling air through it but
the non-vaned SMPS one does not have, as that intended? air will go
through
the path of least resistance over the uncluttered preamp . I can see a
baffle going in here to direct air over this plain block heatsink. Anyone
experience of these little amps?
Both SMPS powerFETs s/c all round. Each has a discoloured patch on the
mounting-plate where the die overlies. No burning/blow-holes of these
powerFET encapsulations or 10R SMD gate droppers or anything else found
suspect from cold testing/close inspection, nor suspect looking PbF. The
SMPS supervisor IC ident is ground off and a schematic for a similar amp
has no ident. I could find details of any 8 pin 0.1 inch pitch package
with
push/pull drive in 1991 DATA linear colated listing- any suggestions for
this sort of search?
p1 supply low side
p3 probably Enable
p4 Vcc
p5 and p7 hi/lo outputs
p6 mid connection to both output powerFET
Does not seem to be any thermal shutdown for the SMPS section




I've got one of those here I gave up on. Life's too short and doesn't pay
enough for this kind of palaver.

Good luck!


Gareth.


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Gareth Magennis wrote in message
...

"N_Cook" wrote in message
...
Mains fuse blew in the middle of normal use.
No mention of PbF anywhere but it is. Unlikely the problem though. Seems
bad
thermal design as audio-out vaned heatsink has cooling air through it

but
the non-vaned SMPS one does not have, as that intended? air will go
through
the path of least resistance over the uncluttered preamp . I can see a
baffle going in here to direct air over this plain block heatsink.

Anyone
experience of these little amps?
Both SMPS powerFETs s/c all round. Each has a discoloured patch on the
mounting-plate where the die overlies. No burning/blow-holes of these
powerFET encapsulations or 10R SMD gate droppers or anything else found
suspect from cold testing/close inspection, nor suspect looking PbF. The
SMPS supervisor IC ident is ground off and a schematic for a similar

amp
has no ident. I could find details of any 8 pin 0.1 inch pitch package
with
push/pull drive in 1991 DATA linear colated listing- any suggestions for
this sort of search?
p1 supply low side
p3 probably Enable
p4 Vcc
p5 and p7 hi/lo outputs
p6 mid connection to both output powerFET
Does not seem to be any thermal shutdown for the SMPS section




I've got one of those here I gave up on. Life's too short and doesn't pay
enough for this kind of palaver.

Good luck!


Gareth.




So what was the failure on your one?


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy



"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N_Cook" wrote in message
...
Mains fuse blew in the middle of normal use.
No mention of PbF anywhere but it is. Unlikely the problem though.
Seems
bad
thermal design as audio-out vaned heatsink has cooling air through it

but
the non-vaned SMPS one does not have, as that intended? air will go
through
the path of least resistance over the uncluttered preamp . I can see a
baffle going in here to direct air over this plain block heatsink.

Anyone
experience of these little amps?
Both SMPS powerFETs s/c all round. Each has a discoloured patch on the
mounting-plate where the die overlies. No burning/blow-holes of these
powerFET encapsulations or 10R SMD gate droppers or anything else found
suspect from cold testing/close inspection, nor suspect looking PbF.
The
SMPS supervisor IC ident is ground off and a schematic for a similar

amp
has no ident. I could find details of any 8 pin 0.1 inch pitch package
with
push/pull drive in 1991 DATA linear colated listing- any suggestions
for
this sort of search?
p1 supply low side
p3 probably Enable
p4 Vcc
p5 and p7 hi/lo outputs
p6 mid connection to both output powerFET
Does not seem to be any thermal shutdown for the SMPS section




I've got one of those here I gave up on. Life's too short and doesn't
pay
enough for this kind of palaver.

Good luck!


Gareth.




So what was the failure on your one?




Both Power amp and Power supply.
Couldn't get a replacement for a blown PSU Mosfet, (Farnell had a one year
waiting list) so subbed in the highest spec one I could find, but it still
didn't power up, (amp disconnected) so I gave up.

If I come across something like this where schematics and parts are not
available, I am not about to spend 6 difficult hours on it, and only be able
to charge 3, so I now cut my losses and refuse.
This, together with muting all TV adverts the past 5 years, has improved my
life immeasurably.


Gareth.



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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

From digeykey filter search , these are 8 pin SMPS ICs , now to see if dual
drive

LTC1041

NJM2103

TDA4605

FAN7680

SG6203





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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Tue, 15 May 2012 16:12:10 +0100, "N_Cook" put
finger to keyboard and composed:

a schematic for a similar amp ...


Could we see it?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Tue, 15 May 2012 16:12:10 +0100, "N_Cook" put
finger to keyboard and composed:

a schematic for a similar amp ...


Could we see it?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.



different powerFET pair but overlay device numbers/types etc correcpond in
the SMPS area otherwise
http://www.eserviceinfo.com/download.php?fileid=51892


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Will jury-rig with a couple of IRF740 in there at 70 percent mains to check
if the supervisor is working.
Can "totem pole" types be used as dual drive? A TDA8130 would go in there
pinning-wise, with 6 of the 8 pins rewired, no idea if correct operational
parameters though. Before trying a pair of 20 amp/600V powerFETs.
Is there any point in roughing the surface of a flat shiney aluminium block
heatsink or painting black for better heat transfer, not really space to add
vanes to the block


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Different heatsink types and different layout to the pics shown in that pdf


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

The SG6203 in that list is totem-pole but the source/sink split is not
available at the output unlike the TDA8130, so none suitable from that
sub-set




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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Wed, 16 May 2012 08:27:42 +0100, "N_Cook" put
finger to keyboard and composed:

Franc Zabkar wrote in message
.. .
On Tue, 15 May 2012 16:12:10 +0100, "N_Cook" put
finger to keyboard and composed:

a schematic for a similar amp ...


Could we see it?


different powerFET pair but overlay device numbers/types etc correcpond in
the SMPS area otherwise
http://www.eserviceinfo.com/download.php?fileid=51892


If I use the following search parameters ...

http://www.google.com/search?q=vb+vs...filetype%3Apdf

.... I get several promising leads, but all of them have the Vcc and
Ground pins interchanged.

http://www.datasheetcatalog.org/data...irf/ir2151.pdf
http://www.irf.com/product-info/data...ta/ir2153z.pdf
http://www.irf.com/product-info/data.../irs27951s.pdf
http://www.dianyuan.com/bbs/u/83/3675811258537068.pdf
http://bbs.dianyuan.com/bbs/u/70/2970761224726220.pdf

.... and lots more.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Wed, 16 May 2012 08:27:42 +0100, "N_Cook" put
finger to keyboard and composed:

Franc Zabkar wrote in message
.. .
On Tue, 15 May 2012 16:12:10 +0100, "N_Cook" put
finger to keyboard and composed:

a schematic for a similar amp ...

Could we see it?


different powerFET pair but overlay device numbers/types etc correcpond

in
the SMPS area otherwise
http://www.eserviceinfo.com/download.php?fileid=51892


If I use the following search parameters ...

http://www.google.com/search?q=vb+vs...filetype%3Apdf

... I get several promising leads, but all of them have the Vcc and
Ground pins interchanged.

http://www.datasheetcatalog.org/data...irf/ir2151.pdf
http://www.irf.com/product-info/data...ta/ir2153z.pdf
http://www.irf.com/product-info/data.../irs27951s.pdf
http://www.dianyuan.com/bbs/u/83/3675811258537068.pdf
http://bbs.dianyuan.com/bbs/u/70/2970761224726220.pdf

... and lots more.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


I tried googling "switch mode" "8 pin" "totem pole"
"switch mode" "8 pin" "hi output" "low output" and similar and found nothing
suitable


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy


"Franc Zabkar"


If I use the following search parameters ...

http://www.google.com/search?q=vb+vs...filetype%3Apdf

... I get several promising leads, but all of them have the Vcc and
Ground pins interchanged.

http://www.datasheetcatalog.org/data...irf/ir2151.pdf
http://www.irf.com/product-info/data...ta/ir2153z.pdf
http://www.irf.com/product-info/data.../irs27951s.pdf
http://www.dianyuan.com/bbs/u/83/3675811258537068.pdf
http://bbs.dianyuan.com/bbs/u/70/2970761224726220.pdf



** The Italian schem may well contain a drawing error re pins 1 and cos
the IR2151 certainly looks the part.

Also, the amplifier output stage is NOT well protected from a short -
those 6.2 V zeners are not gonna save any of the IRFP mosfets, which BTW
need to be matched sets in order to share current.

PLUS, once the power amp fails short from rail to rail - the PSU has got
only one option.

It blows up.

Wot a dago piece of ****.



.... Phil




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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Wed, 16 May 2012 08:27:42 +0100, "N_Cook" put
finger to keyboard and composed:

Franc Zabkar wrote in message
.. .
On Tue, 15 May 2012 16:12:10 +0100, "N_Cook" put
finger to keyboard and composed:

a schematic for a similar amp ...

Could we see it?


different powerFET pair but overlay device numbers/types etc correcpond

in
the SMPS area otherwise
http://www.eserviceinfo.com/download.php?fileid=51892


If I use the following search parameters ...

http://www.google.com/search?q=vb+vs...filetype%3Apdf

... I get several promising leads, but all of them have the Vcc and
Ground pins interchanged.

http://www.datasheetcatalog.org/data...irf/ir2151.pdf
http://www.irf.com/product-info/data...ta/ir2153z.pdf
http://www.irf.com/product-info/data.../irs27951s.pdf
http://www.dianyuan.com/bbs/u/83/3675811258537068.pdf
http://bbs.dianyuan.com/bbs/u/70/2970761224726220.pdf

... and lots more.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


I checked the pcb traces and pins 1 and 4 are swapped over on that schematic
, the 270K dropper agrees but ground and supply are swapped so pinning
agreement with those IR... ones


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Would you trust amp repair to a company where they pull knobs away with
carpenter's pliers?
I assume that is the reason for the ground off ident, to lock into their
repair shop




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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy


"N_Cook"

I checked the pcb traces and pins 1 and 4 are swapped over on that
schematic
, the 270K dropper agrees but ground and supply are swapped so pinning
agreement with those IR... ones



** Told ya ....



..... Phil


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

With 2x IRF740 in there and 60 percent mains there is high current draw,
some smps type oscillator start up noise and mains draw current drops right
back with 180V over the main bridge rect , switch off and that 180V takes a
long time dropping to 150V with some low level audible osc type noise . No
led or fan tries turning , perhaps needs more than 60 percent for this or
something else wrong, will have to try monitoring SMPS output before
venturing higher


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Wed, 16 May 2012 12:34:31 +0100, "N_Cook" put
finger to keyboard and composed:

I checked the pcb traces and pins 1 and 4 are swapped over on that schematic
, the 270K dropper agrees but ground and supply are swapped so pinning
agreement with those IR... ones


If you measure the Vcc of the IC, then that should narrow down the
suitable candidates. Vcc is determined by an internal zener, not by
the external components. It doesn't sound like this IC is the problem,
though.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Wed, 16 May 2012 12:34:31 +0100, "N_Cook" put
finger to keyboard and composed:

I checked the pcb traces and pins 1 and 4 are swapped over on that

schematic
, the 270K dropper agrees but ground and supply are swapped so pinning
agreement with those IR... ones


If you measure the Vcc of the IC, then that should narrow down the
suitable candidates. Vcc is determined by an internal zener, not by
the external components. It doesn't sound like this IC is the problem,
though.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.



When I get back to it I will try a 72V zener over one of the Brown-out?
zener chain of 220/200V zeners, while srill trying with 60 percent mains (2
x200V caps across the main DC - reminder to myself to find a workaday
formula for "Vz" of zeners at 1/10 to 1/10000 of rated current )


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Thu, 17 May 2012 08:13:30 +0100, "N_Cook" put
finger to keyboard and composed:

When I get back to it I will try a 72V zener over one of the Brown-out?
zener chain of 220/200V zeners ...


I would think that 420VDC would be required to "turn on" the series
connected zener pair. A 240VAC source would produce 350VDC, so ISTM
that these zeners would be sensing an overvoltage rather than a
brownout. That said, the overvoltage would have to be an extremely
large one (+20%).

- Franc Zabkar
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Thu, 17 May 2012 08:13:30 +0100, "N_Cook" put
finger to keyboard and composed:

When I get back to it I will try a 72V zener over one of the Brown-out?
zener chain of 220/200V zeners ...


I would think that 420VDC would be required to "turn on" the series
connected zener pair. A 240VAC source would produce 350VDC, so ISTM
that these zeners would be sensing an overvoltage rather than a
brownout. That said, the overvoltage would have to be an extremely
large one (+20%).

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


That 47K must put the current into the uA regime
I doubt the Ebers-Moll sort of stuff applies in this sort of illegitimate
area of operation.
Tried a 6.2V 1W zener
Vz 6.22V (initially then rising) @ 78mA
96 percent of Vz @ 7.4mA
95% @ 810uA
92% @ 102uA
77% @ 9.6uA
66% @ 2.6uA (4.12V)


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

I'd forgotten to at least try the PA and its ok up to +/-25V dc on a bench
PS , 63V rated caps, so less than the 80V of that schematic.
The PA is certainly different to that schematic, pair of those 5 pin SAP
devices with intimate thermally connected sensing diodes


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

470K not 47K

I thought startup was a bit quiet, somewhere along the way I've managed to
short G-S on the high side IRF740. The other one changes state on DVM
"diode" test. Shorted turns on the switch mode transformer ? Change C68,
perhaps punch through ?


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

A dropper will go in with changed 1uF and new sacrificial IRF740 tomorrow
1KHz RLC testing of the Tx
feedback coil .039mH
240V tap 2.37mH to gnd
230V tap 2.22mH
100V 1.8mH looks reasonable

Along the way that Zener3 in the 200+220V zener chain is probably 6.2V (at
low uA level) and the 2N7002 (SMD topcode mark 782 R) functions as it should


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Thu, 17 May 2012 16:42:56 +0100, "N_Cook" put
finger to keyboard and composed:

Along the way that Zener3 in the 200+220V zener chain is probably 6.2V (at
low uA level) and the 2N7002 (SMD topcode mark 782 R) functions as it should


AISI, the 2N7002 FET should be off in normal operation, so I think
you're wasting your time in this area. If you're concerned about the
"Drive IC's" Enable pin, then disconnect D37.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

Franc Zabkar wrote in message
...
On Thu, 17 May 2012 16:42:56 +0100, "N_Cook" put
finger to keyboard and composed:

Along the way that Zener3 in the 200+220V zener chain is probably 6.2V

(at
low uA level) and the 2N7002 (SMD topcode mark 782 R) functions as it

should

AISI, the 2N7002 FET should be off in normal operation, so I think
you're wasting your time in this area. If you're concerned about the
"Drive IC's" Enable pin, then disconnect D37.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


I agree, there is another associted point. There is no jumper configuration
in that area for 100/120V countries so must be completely inoperative , in
mormal operation, in those countries


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

I suppose for this amp only used in 240V land, then replacement SMPS driver
powerFETs only need to be rated 600V/10A and for such an amp only in
100/110/120V land then 300V/20A rating


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy


"Nut case Kook is off his rocker "


I suppose for this amp only used in 240V land, then replacement SMPS driver
powerFETs only need to be rated 600V/10A and for such an amp only in
100/110/120V land then 300V/20A rating



** ROTFLMAO !!!!!!!!!!!!!!!!

Go look at the ****ing CIRCUIT !!

Idiot !!!






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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

I've acquired a new IR2153 and desoldered the original unkown driver and as
the Tx primaries are some distance from the driver IC, soldered in a turned
pin socket. The old one has Thailand and R3 mould marks on the underside and
perhaps the second line on the top starts with a 7 and the third line ends
with a 5 . I'm assuming there was a top line that is well ground out.
Will power up with a couple of droppers in there with 60 percent mains ,
still set on 240V jumper.
I can now compare old and putative replacement


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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

A bit further forward I suppose. Exactly the same, for 2153 and original,
audible low level oscillator noise , 10 seconds or so after switch off
presumably coming down from ultrasonic and dropping in pitch over a couple
of minutes while there is HV in the main caps. And +/-0.5V on the main rail
caps transfered across the Tx from the startup pulses, instead of the +/-60V
or so . But no sustained drive. Next is some monitor of the Tx primary
feedback route to the driver and somehow monitor the osc f, perhaps change
the SM cap is easier, the SMRs measure ok. Any tricks for fooling the driver
into thinking there is more feedback than actual, a battery wired-in?




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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Fri, 18 May 2012 08:49:52 +0100, "N_Cook" put
finger to keyboard and composed:

I suppose for this amp only used in 240V land, then replacement SMPS driver
powerFETs only need to be rated 600V/10A and for such an amp only in
100/110/120V land then 300V/20A rating


JP1 in the bridge rectifier area configures the unit for 240VAC
operation when open, and 120VAC when closed. In the latter case the
circuit becomes a voltage doubler.

Therefore Vdc = 350VDC in both configurations.

- Franc Zabkar
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Fri, 18 May 2012 16:12:40 +0100, "N_Cook" put
finger to keyboard and composed:

A bit further forward I suppose. Exactly the same, for 2153 and original


I would have done a bit more testing before I opted for the 2153.

For example, I would have disabled the "Driver IC5" by shorting the
drain and source pins of T24 with a blob of solder (assuming a GDS
pinout). This would allow the Vcc capacitor (C52) to charge to the
IC's internal zener voltage. You could then compare this voltage
against the datasheet.

If the IC is oscillating, then this frequency may also provide a clue
to the chip's identity.

- Franc Zabkar
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Default 250W amp - Mark Bass , Little Mark 250, of 2008, Italy

On Fri, 18 May 2012 16:12:40 +0100, "N_Cook" put
finger to keyboard and composed:

A bit further forward I suppose. Exactly the same, for 2153 and original,
audible low level oscillator noise , 10 seconds or so after switch off
presumably coming down from ultrasonic and dropping in pitch over a couple
of minutes while there is HV in the main caps. And +/-0.5V on the main rail
caps transfered across the Tx from the startup pulses, instead of the +/-60V
or so . But no sustained drive. Next is some monitor of the Tx primary
feedback route to the driver and somehow monitor the osc f, perhaps change
the SM cap is easier, the SMRs measure ok. Any tricks for fooling the driver
into thinking there is more feedback than actual, a battery wired-in?


I'm having some difficulty understanding your plan, but first allow me
to explain how I think the circuit works. If I'm wrong, someone will
hopefully correct me.

Firstly, I would not attempt to substitute a battery for the
"feedback" voltage. This will defeat the IC's overload protection. If
you are going to do this, at least disconnect the 1uF capacitor (C68).
Also, instead of a battery, you could add several 270K feed resistors
between Vdc and Zener3. Then monitor the IC's Hi and Lo outputs. That
should at least give you some confidence in the IC.

As for how the IC works, I believe it would have a start mode and a
run mode. In the start mode it would draw a very small current,
probably less than 1mA. This would allow the Vcc capacitor (C52) to
charge. When Vcc exceeds the undervoltage lockout threshold, the IC
switches to run mode. It then attempts to kickstart the supply by
pulsing the MOSFETs. In run mode the IC would draw more current than
can be provided by R78, in which case C52 would begin to discharge. If
a regenerated supply cannot be developed from a secondary transformer
winding via D34, C69, D21, and C70, then C52 will discharge to below
the lockout threshold, causing the IC to revert to start mode. C52
then charges once again, and so on.

Therefore, if there is an overload on the secondaries, the regenerated
supply never eventuates, and the IC hiccups. Some IC's will count the
number of hiccups and shut down completely if there are too many
attempts.

- Franc Zabkar
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Franc Zabkar wrote in message
...
On Fri, 18 May 2012 16:12:40 +0100, "N_Cook" put
finger to keyboard and composed:

A bit further forward I suppose. Exactly the same, for 2153 and original


I would have done a bit more testing before I opted for the 2153.

For example, I would have disabled the "Driver IC5" by shorting the
drain and source pins of T24 with a blob of solder (assuming a GDS
pinout). This would allow the Vcc capacitor (C52) to charge to the
IC's internal zener voltage. You could then compare this voltage
against the datasheet.

If the IC is oscillating, then this frequency may also provide a clue
to the chip's identity.

- Franc Zabkar
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I am getting very inconsistent poor to bad ESR with electroC69 so will
change that and C70.



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The 2153 has Thailand in a dimple on the rear of the package and an empty
dimple on the diagonal, this structure the same as the ground off one, minus
the R 3 .
I wonder how many IR 8pin , that pinning packages , were available in 2008
and a year or two before. Unfortunately I don't like using isolation
transformers and scopes on SMPS to narrow down a bit more, if I regularly
dealt with SMPS failures then perhaps it would be different. If this one
wasn't a lot of difficult to probe SM around the DIP8 SMPS driiver ,hemmed
in by heatsinks and large caps then may have been different






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On Sat, 19 May 2012 09:10:14 +0100, "N_Cook" put
finger to keyboard and composed:

I am getting very inconsistent poor to bad ESR with electroC69 so will
change that and C70.


Those capacitors are a common reason for failure to start. Sorry, I
assumed you would have checked them.

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Franc Zabkar wrote in message
...
On Fri, 18 May 2012 08:49:52 +0100, "N_Cook" put
finger to keyboard and composed:

I suppose for this amp only used in 240V land, then replacement SMPS

driver
powerFETs only need to be rated 600V/10A and for such an amp only in
100/110/120V land then 300V/20A rating


JP1 in the bridge rectifier area configures the unit for 240VAC
operation when open, and 120VAC when closed. In the latter case the
circuit becomes a voltage doubler.

Therefore Vdc = 350VDC in both configurations.

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So that 220/220V zener chain is perhaps more for the possibility of someone
jumpering JP1 to 100V and plugging in to 240V and instead of 350V dc trying
to get to 700V dc

Have got inundated with more normal stuff and this Mark will have to wait a
few days




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I now see someone else has been here before and ground off IC5

music-electronics-forum.com/t10881/

What is the difference between IR2153 and IR21531?
The original has a diode between Vcc and VB so perhaps whether 2153 or 21531
or any other IR it should be the D variant or adding a high voltage diode
externally


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On Sat, 19 May 2012 11:29:12 +0100, "N_Cook" put
finger to keyboard and composed:

So that 220/220V zener chain is perhaps more for the possibility of someone
jumpering JP1 to 100V and plugging in to 240V and instead of 350V dc trying
to get to 700V dc


Ah, that would make sense. I was wondering why there was a 275V MOV
across A-N, since that voltage would be below the overvoltage
threshold for the zener chain.

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On Sat, 19 May 2012 13:52:58 +0100, "N_Cook" put
finger to keyboard and composed:

I now see someone else has been here before and ground off IC5

music-electronics-forum.com/t10881/


Did you see the following post in that thread?

================================================== ==================
Have you noticed that pins 1 and 4 (Vcc and COM) of IC5 are reversed
on the schematic (if this is IR21531)?
================================================== ==================

I noticed on the one i'm working on. I was hoping it was an error in
the schematic but it is not.

I verifyed continuity to ground at pin 1.

So the IR21531 is not a drop in replacement as far as I can tell. I
have looked at just about every self oscilating half bridge drive they
sell and nothing that has pins 1 and 4 swapped.
================================================== ==================

- Franc Zabkar
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