My 2230 scope suddenly died the other day.

It's a great piece of equipment and I would like to repair it (if possible) or
pay for it to be repaired if economically viable. I have a contact in the TV
repair trade who may be able to help (he repairs switcher PSUs regularly).

Does anyone know of any companies in the UK which specialise in the repair of
Tek scopes?

I'm pretty certain that the PSU has blown. The fuse blew and and the unit
blows replacement fuses. The fan doesn't come on and the front power LED
doesn't come on.

I opened up the scope and it appears that the PSU is part of the large bottom
PCB. It appears to be well connected to the front panel. It looks like you
have to know what you are doing to safely extract the PCB to even examine the
PSU area. Any suggestions are welcome.

Which other Tek scopes share the same PSU design?

I have already googled for "2230 repair" but it might be helpful to try for
similar faults on related scopes.

regards...

--Gary

Gary Morton wrote in
news
My 2230 scope suddenly died the other day.

It's a great piece of equipment and I would like to repair it (if
possible) or
pay for it to be repaired if economically viable. I have a contact
in the TV
repair trade who may be able to help (he repairs switcher PSUs
regularly).

Does anyone know of any companies in the UK which specialise in the
repair of Tek scopes?

I'm pretty certain that the PSU has blown. The fuse blew and and the
unit blows replacement fuses. The fan doesn't come on and the front
power LED doesn't come on.

I opened up the scope and it appears that the PSU is part of the large
bottom PCB. It appears to be well connected to the front panel. It
looks like you have to know what you are doing to safely extract the
PCB to even examine the PSU area. Any suggestions are welcome.

First,you don't extract the main board to service the PS.(a major PITA)
You can remove the PS shield(cage) and bottom cover and work on it
(unsolder) from the bottom. The problem is most likely to be bad
electrolytics (ESR),shorted rectifier diodes,and/or the pre-reg FET(on a
small heat sink) is probably shorted. The FET should be soldered to the 3-
wire ribbon cable,its Molex connector should have been removed by a field
mod when serviced(at TEK).Other failures could be the power oscillator
transistors(shorted or open,along with their base resistors,or the pre-reg
overvoltage crowbar;a bad 51v zener,open 3 ohm fusible R,or shorted SCR.
A less likely possibility is a bad HV multiplier.

Which other Tek scopes share the same PSU design?

2213,2215,2235,2236,same general architecture.Components may be labelled
differently. 2230,2235/36 have higher anode V,IIRC.

I have already googled for "2230 repair" but it might be helpful to
try for similar faults on related scopes.

regards...

--Gary



The 2230 uses a pre-regulator based on a TL494 or TL594 IC to knock
rectified line V (90-250 VAC input) down to ~43vDC, to a power oscillator
that creates the secondary low voltages and the HV cathode and anode
supplies.

You must use an isolation XFMR to scope the primary side of the PS.

Incidentally,this scope PCB was stuffed on an automated insertion
machine,wave soldered,and sliced into pieces,the front panel PCB remaining
attached to the main board.

--
Jim Yanik
jyanik-at-kua.net

Jim Yanik wrote:

....snip...


First,you don't extract the main board to service the PS.(a major PITA)
You can remove the PS shield(cage) and bottom cover and work on it
(unsolder) from the bottom. The problem is most likely to be bad
electrolytics (ESR),shorted rectifier diodes,and/or the pre-reg FET(on a
small heat sink) is probably shorted. The FET should be soldered to the 3-
wire ribbon cable,its Molex connector should have been removed by a field
mod when serviced(at TEK).Other failures could be the power oscillator
transistors(shorted or open,along with their base resistors,or the pre-reg
overvoltage crowbar;a bad 51v zener,open 3 ohm fusible R,or shorted SCR.
A less likely possibility is a bad HV multiplier.


....snip...

Jim,

thanks for your reply.

I've just been trying to remove the PSU cage, but so far I haven't succeeded.
In fact I can't really see how it will lift out as the turned over edges of
the side and back panel will block it. I can see why repairs could be so
expensive as it looks like it can take a lot of time to get to the faulty
board! I've removed all the obvious screws, but something still seems to br
holding the cage back, so I can't even try to manipulate it. I would hate to
have to take off the side and rear metal panel as the rear appears to support
the CRT and I would be scared of damaging it.

On the bottom Q947 and Q946 look as if they have been resoldered (and there is
a strange flux residue). I'm assuming that they get so hot (possibly due to
the fault) that the solder melts.

I've found some of your other posts which describe problems with the 2235 PSU,
so if I can actually get at the parts I feel that there is a possibility (with
help) that I may be able to get it fixed.

If I get it open I will describe anything looking obviously broken.

regards...

--Gary

Gary Morton wrote in message ...

thanks for your reply.

I've just been trying to remove the PSU cage, but so far I haven't succeeded.
In fact I can't really see how it will lift out as the turned over edges of
the side and back panel will block it. I can see why repairs could be so
expensive as it looks like it can take a lot of time to get to the faulty
board! I've removed all the obvious screws, but something still seems to br
holding the cage back, so I can't even try to manipulate it. I would hate to
have to take off the side and rear metal panel as the rear appears to support
the CRT and I would be scared of damaging it.

On the bottom Q947 and Q946 look as if they have been resoldered (and there is
a strange flux residue). I'm assuming that they get so hot (possibly due to
the fault) that the solder melts.

I've found some of your other posts which describe problems with the 2235 PSU,
so if I can actually get at the parts I feel that there is a possibility (with
help) that I may be able to get it fixed.

If I get it open I will describe anything looking obviously broken.

regards...

--Gary

In case you still run into problems, I can offer a service addres near.

let us know in the NG, how you succeed.

hth,
Andreas