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 Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display

Hi to all the people here

I bought the old preamplifier,i remember it as pretty silent,and the
"apparent" S/N ratio is further increased by the proprietary noise gate
called "H.U.S.H."
This is a good pic of the board ,found on a website
https://images.reverb.com/image/uplo...aqvapl3ygx.jpg
I'm finding it a bit too noisy,and this noise sounds as "digital
noise",more than white noise..it sounds like the frequencies composing the
noise are related to the activity of the segments digits of the
display.Adding a piece of wire as antenna to the resistors between IC
driver and display increases some particular frequency to the heared
noise,confirming my impression .
I tried shorting ground points with good cables,it does not change
anything.
I tried adding some metallic shield with minimal or null impact.
I ask your opinion about the decoupling capacitors,they are 1uF ceramic
capacitors,with relatively long leads.Do yout think that it is worth
replacing them?Maybe with SMD capacitor directly to IC VDD and GND?
Another idea is to replace the displays with new ones more
efficient,needing much less current,and then ,to increase the resistor
values,less current=less noise,but i still dont know if such display
exists.
I would like to know your opinion.
Thanks for your time
Diego

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Default Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display


Another idea is to replace the displays with new ones more
efficient,needing much less current,and then ,to increase the resistor
values,less current=less noise,but i still dont know if such display
exists.
I would like to know your opinion.
Thanks for your time
Diego

---
Questa email è stata esaminata alla ricerca di virus da AVG.
http://www.avg.com


what type of display LED?

can you use standard signal tracing to determine which audio stage is picking up the noise, does the volume control effect it, tone controls etc.
?
m

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Default Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display

On Monday, 1 July 2019 16:36:27 UTC+1, blisca wrote:
Hi to all the people here

I bought the old preamplifier,i remember it as pretty silent,and the
"apparent" S/N ratio is further increased by the proprietary noise gate
called "H.U.S.H."
This is a good pic of the board ,found on a website
https://images.reverb.com/image/uplo...aqvapl3ygx.jpg
I'm finding it a bit too noisy,and this noise sounds as "digital
noise",more than white noise..it sounds like the frequencies composing the
noise are related to the activity of the segments digits of the
display.Adding a piece of wire as antenna to the resistors between IC
driver and display increases some particular frequency to the heared
noise,confirming my impression .
I tried shorting ground points with good cables,it does not change
anything.
I tried adding some metallic shield with minimal or null impact.
I ask your opinion about the decoupling capacitors,they are 1uF ceramic
capacitors,with relatively long leads.Do yout think that it is worth
replacing them?Maybe with SMD capacitor directly to IC VDD and GND?
Another idea is to replace the displays with new ones more
efficient,needing much less current,and then ,to increase the resistor
values,less current=less noise,but i still dont know if such display
exists.
I would like to know your opinion.
Thanks for your time
Diego


The simple way to find out if replacing a cap will help is to bridge it with another cap. If the original is ok, it makes no difference. If the original is bad, it solves the problem. Sometimes you can just hold the 2nd cap & touch it onto other caps one after another to dx a fault.


NT
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Default Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display

On 7/10/19 9:18 AM, wrote:
On Monday, 1 July 2019 16:36:27 UTC+1, blisca wrote:
Hi to all the people here

I bought the old preamplifier,i remember it as pretty silent,and
the "apparent" S/N ratio is further increased by the proprietary
noise gate called "H.U.S.H." This is a good pic of the board ,found
on a website
https://images.reverb.com/image/uplo...aqvapl3ygx.jpg


I'm finding it a bit too noisy,and this noise sounds as "digital
noise",more than white noise..it sounds like the frequencies
composing the noise are related to the activity of the segments
digits of the display.Adding a piece of wire as antenna to the
resistors between IC driver and display increases some particular
frequency to the heared noise,confirming my impression . I tried
shorting ground points with good cables,it does not change
anything. I tried adding some metallic shield with minimal or null
impact. I ask your opinion about the decoupling capacitors,they are
1uF ceramic capacitors,with relatively long leads.Do yout think
that it is worth replacing them?Maybe with SMD capacitor directly
to IC VDD and GND? Another idea is to replace the displays with new
ones more efficient,needing much less current,and then ,to increase
the resistor values,less current=less noise,but i still dont know
if such display exists. I would like to know your opinion. Thanks
for your time Diego


The simple way to find out if replacing a cap will help is to bridge
it with another cap. If the original is ok, it makes no difference.
If the original is bad, it solves the problem. Sometimes you can just
hold the 2nd cap & touch it onto other caps one after another to dx a
fault.


That's a great way to blow stuff up, too.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com



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Default Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display

On Wednesday, 10 July 2019 15:40:24 UTC+1, Phil Hobbs wrote:
On 7/10/19 9:18 AM, tabbypurr wrote:
On Monday, 1 July 2019 16:36:27 UTC+1, blisca wrote:


Hi to all the people here

I bought the old preamplifier,i remember it as pretty silent,and
the "apparent" S/N ratio is further increased by the proprietary
noise gate called "H.U.S.H." This is a good pic of the board ,found
on a website
https://images.reverb.com/image/uplo...aqvapl3ygx.jpg


I'm finding it a bit too noisy,and this noise sounds as "digital
noise",more than white noise..it sounds like the frequencies
composing the noise are related to the activity of the segments
digits of the display.Adding a piece of wire as antenna to the
resistors between IC driver and display increases some particular
frequency to the heared noise,confirming my impression . I tried
shorting ground points with good cables,it does not change
anything. I tried adding some metallic shield with minimal or null
impact. I ask your opinion about the decoupling capacitors,they are
1uF ceramic capacitors,with relatively long leads.Do yout think
that it is worth replacing them?Maybe with SMD capacitor directly
to IC VDD and GND? Another idea is to replace the displays with new
ones more efficient,needing much less current,and then ,to increase
the resistor values,less current=less noise,but i still dont know
if such display exists. I would like to know your opinion. Thanks
for your time Diego


The simple way to find out if replacing a cap will help is to bridge
it with another cap. If the original is ok, it makes no difference.
If the original is bad, it solves the problem. Sometimes you can just
hold the 2nd cap & touch it onto other caps one after another to dx a
fault.


That's a great way to blow stuff up, too.

Cheers

Phil Hobbs


how? I never have that way. Obviously some clue is required, not applying a 400v charged cap to a base somewhere.


NT
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