Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I have a topward dual power supply the left side doesn't get up to full voltage.
If you look in the swap meet section there is some discussion pictures and schematics.

I had an idea that maybe since there aren't that many parts just order some stuff and shotgun it.

However after reading about these units I saw a few instances where some transistor replacements fixed the problem(s).

So for the sake of clarity the focus of this discussion is to simply focus on transistors for the preliminary investigation.

Reading some old threads I saw where I can probe the collector and emitter of said devices in circuit and check for shorts. 
-if there is no short then move along
-if there is a short it may be good because of the circuit but remove and test

If I have interpreted this correctly I like this plan  :tu: because for starters the power is OFF.  :lmao:

Also it will give me some experience discerning a voltage regulator from a transistor  :loco

So if you like that then that is my plan nothing more or less.  Just check every transistor in circuit for C-E short and report back.

Can you put up a link to the previous posts?

https://www.ssguitar.com/index.php?topic=5354.0

Lord I was born a rambling man (below):

I tried to find a source for the relay(s) even contacting one established high volume vendor and they didn't have an exact match.

Also some of the Internet lore indicates this PS works on a "break before make" (or vice versa) and is somewhat complicated. 

I had seen an advantage to having "the same" boards on each side" (remember working on drum brakes  :tu: ) but the two sides may not be identical)

Also the schematic (for the digital meter version) I don't see any test voltages anywhere  :loco but maybe I missed them idk.

Anyhow I want to try and keep it simple and do some fundamental inspections without opening a can of worms.  xP

Without looking at the schem.,I would guess that the two sides are the same, so you should be able to compare readings on transistors etc. to the good side.

This will be good.  I hope I dont report back with tales of falsely accused to-220 voltage regulators  :loco

Ok guys did a little snooping around after work...compiled a list of transistors from the board.
IMG_20241208_184416104.jpg

I checked all of them in diode/continuity mode and the testing was uneventful then crazy the last one I checked  :grr I am focusing on.
Because the outer legs had a low (0.09v) voltage readings.
IMG_20241208_184439644.jpg

I thought I was losing my mind until I remember they are like diodes and POS and neg leads matter...doh

But I compiled a summary of my examination of this particular device aka Q26
IMG_20241208_190136226 (1).jpg

So it's not much but it's something  :lmao:  :'(

But now I'm thinking it must be a result of the circuit that it is in.

 :'(

Time to look at the schematic  xP

Oh well nm  xP

Looks like I got some component removal and replacement practice
IMG_20241209_112111625 (1).jpg

I replaced the 1815 and it didn't fix the problem and all of the in circuit readings are identical

But ..at least it still "works"  :loco

Before I buttoned it up I poked around a few capacitaters looking for direct shorts 🩳 to no avail.

I'm back to "dude...it's the relay"

IMG_20241209_121942351.jpg

I was gonna try to 🦘 jump it but figured I would quit while I was ahead....or in the same place  :loco

Meanwhile WOW what a transformer  :dbtu:
IMG_20241209_124230902_HDR.jpg

 :tu: