Ever wished that Randall had gone just the extra inch and added a 'Reverb' foot-switch to their FS-5 Channel Switching foot-switch that came with their RG100-ES's?

Well, with a couple of parts from Amazon...you can.

These are the parts I purchased from Amazon to add the Reverb foot-switch to my existing FS-5.(see photos for details)

Rather than write a 5 paragraph essay here. Just shoot me any questions you may have and I'll get back to you ASAP.

These are well worth their weight in gold. And very easy to build.

Does anybody know of anyone that actually makes and sells these??

Quote from: Miyagi_83 on December 11, 2024, 05:38:50 PMOk, here's your voltage chart with added readings of requested transistors.
Looking at the numbers on the diagram, measurements for Q11 make sense to me. Those for Q12 don't. Take a look:
The collector of Q11 is connected straight to the +41V rail. According to your readings, the collector of Q12 is at +41V too, which suggests those two terminals are connected, but they shouldn't be. Q12 is in the negative leg of the power supply, so IMHO its collector should be negative in relation to ground. Unless there is a mistake in labelling of course.

Let's look at Q10 now. According to the schematic, its base is tied to the collector of Q8 and R41. R41 is tethered to the positive power supply rail. The original schematic shows a value of 38 V at the collector of Q8 and, consequently, base of Q10.

Personally, I would try to track the connections between different components on the PCB and compare my findings to the schematic so as to establish what is what and what connects to what. It'd be time-consuming and probably frustrating, I know, but I'd do that nonetheless. Perhaps it's unnecessary, I don't know. Let's wait for the more experienced players to chime in.

Here's my $0.02.

I am going to take your advise and reverse engineer the PCB with a bright backlight and see how the components are TRULY connected once and for all. It'll be a good day or two. I'm going to take my time and triple check everything before posting my findings.

Quote from: Miyagi_83 on December 11, 2024, 04:54:01 PM

Quote from: RG100ESROX on December 11, 2024, 01:27:02 PMAs you can see...where I once had -.6 (as indicated on the schematic) is now +.521v. I don't even know how this is possible. But, this is the case.

Now, if I look at the back side of the PCB. I honestly do not see how the bias trim pot can be located in the circuit as indicated in the schematic. However, and again, I used to get -.6VDC on the bottom lug of the bias trim pot as it is indicated on the schematic before I broke the amp. So, how does it go from -.6VDC to +.521?

Are you absolutely, 100% sure that it used to be -.6VDC and not +.6VDC? Are you certain that your memory and / or notes serve you well on this one? If that particular leg of the trim pot is connected to the base of Q11, and it seems it is, at least judging by the voltage readings, according to the original circuit diagram there should be and should have been a positive voltage there. What's more, the original schematic says the voltage there should be roughly twice that, it says 1.2 V on the schematic, after all.

You are correct about the voltage. There is supposed to be +1.2v on Q10 and Q11, and -.6v on the trim pot. That's why I found it interesting that the voltage was the same at those two points in the circuit, and that's why I highlighted them in yellow. None of it makes any sense to me at all. Now, I cannot verify that the voltage used to be +1.2, because I don't remember checking it. But, I absolutely  remember checking the trim pot at the noted location many times, and it WAS -.6v.

Quote from: Miyagi_83 on December 11, 2024, 04:54:01 PM

Quote from: RG100ESROX on December 11, 2024, 01:27:02 PMAs you can see...where I once had -.6 (as indicated on the schematic) is now +.521v. I don't even know how this is possible. But, this is the case.

Now, if I look at the back side of the PCB. I honestly do not see how the bias trim pot can be located in the circuit as indicated in the schematic. However, and again, I used to get -.6VDC on the bottom lug of the bias trim pot as it is indicated on the schematic before I broke the amp. So, how does it go from -.6VDC to +.521?

Are you absolutely, 100% sure that it used to be -.6VDC and not +.6VDC? Are you certain that your memory and / or notes serve you well on this one? If that particular leg of the trim pot is connected to the base of Q11, and it seems it is, at least judging by the voltage readings, according to the original circuit diagram there should be and should have been a positive voltage there. What's more, the original schematic says the voltage there should be roughly twice that, it says 1.2 V on the schematic, after all.

Absolutely sure. 101%....

If you notice on the schematic it actually denotes -.6v at that point on the trim pot. I measured it many times before breaking the amp and it was -.566v when the trim pot was FCCW.

Quote from: Miyagi_83 on December 11, 2024, 03:37:54 PM

Quote from: RG100ESROX on December 11, 2024, 01:27:02 PMAnyway, let me know what you think, and if you need any further clarification or additional voltage readings.

Jay, I'd like to ask you to measure voltages at the following points:
1. base and emitter of Q10
2. collector and emitter of Q11
3. collector and emitter of Q12

I suspect we'll need to rearrange the schematic. I suspect the same...

TIP 31C/32C
  B1/C2/E3

1. base and emitter of Q10 - B = -.697 E = -.089
2. collector and emitter of Q11 - C = +41.22 E = -.040 
3. collector and emitter of Q12 - C = +.510 E = +41.04

Quote from: Miyagi_83 on December 11, 2024, 03:53:15 PMIs there a meaning to the short red line below the trim pot and the red dot between the yellow-filled oval and Q12 on the schematic excerpt you posted?

Yes. I was just denoting that I found it interesting that these two points in the circuit shared the same voltage reading....

Here are the bias string voltages.

As you can see...where I once had -.6 (as indicated on the schematic) is now +.521v. I don't even know how this is possible. But, this is the case.

Now, if I look at the back side of the PCB. I honestly do not see how the bias trim pot can be located in the circuit as indicated in the schematic. However, and again, I used to get -.6VDC on the bottom lug of the bias trim pot as it is indicated on the schematic before I broke the amp. So, how does it go from -.6VDC to +.521?

Anyway, let me know what you think, and if you need any further clarification or additional voltage readings.

Thanks in advance, M.

-Jay

Quote from: Miyagi_83 on December 10, 2024, 03:19:24 PM

Quote from: RG100ESROX on December 10, 2024, 02:41:28 PM Here ya go!!!

Thank you, sir.
I understand that point A is roughly the same as point B, only positive. This means it was simply mislabelled in the bias-string-voltage pic posted earlier. Therefore, I would like to kindly ask you to measure and write down the voltages along the bias string again, but please don't rush it, focus, and note down everything correctly so we don't spend time looking for solutions to non-existent problems.
Looking forward to it.
M.

No. Thank YOU!!

Will do. It'll be later this afternoon , but I'll take my time and get them posted as soon as possible.

Quote from: RG100ESROX on December 10, 2024, 10:00:55 AM

Quote from: Miyagi_83 on December 10, 2024, 04:32:41 AM

Quote from: RG100ESROX on November 25, 2024, 06:51:19 PM

Quote from: g1 on November 25, 2024, 03:37:05 PMThat's fine if you had the gen. set for low level output.
Check the amps power supply (DC)voltages, shown as  A,B,C,D,E on the schematic.

VOLTAGES REQUESTED: Here ya go!

A =  41.90VDC  = +41.18VDC
B = -41.60VDC  = -41.22VDC
C =  12.61VDC  = +12.45VDC
D = -12.60VDC  = -12.45VDC
E =  25.38VDC  =+25.19VDC

I found them. 2 weeks ago they were fine, so you might have made a mistake in your labelling, but do check again, just to be sure.

Edit: BTW, do you have another voltmeter on hand that you could try? I do, and I have determined that they both provide the same voltage readings down to .01 volts. The incorrect readings might be caused by a number of factors. Faulty or poor-quality test equipment, faulty component(s) in the circuit, or human error come to mind. Oh, we know all about this...  (-;

Here ya go!!!

Quote from: Miyagi_83 on December 10, 2024, 04:32:41 AM

Quote from: RG100ESROX on November 25, 2024, 06:51:19 PM

Quote from: g1 on November 25, 2024, 03:37:05 PMThat's fine if you had the gen. set for low level output.
Check the amps power supply (DC)voltages, shown as  A,B,C,D,E on the schematic.

VOLTAGES REQUESTED: I will get these voltage readings for you later this morning.

A =  41.90VDC
B = -41.60VDC
C =  12.61VDC
D = -12.60VDC
E =  25.38VDC

I found them. 2 weeks ago they were fine, so you might have made a mistake in your labelling, but do check again, just to be sure.

Edit: BTW, do you have another voltmeter on hand that you could try? I do, and I have determined that they both provide the same voltage readings down to .01 volts. The incorrect readings might be caused by a number of factors. Faulty or poor-quality test equipment, faulty component(s) in the circuit, or human error come to mind. Oh, we know all about this...  (-;

Quote from: Miyagi_83 on December 10, 2024, 12:31:11 AM

Quote from: RG100ESROX on December 09, 2024, 06:52:06 PMThe RCA connectors for the reverb have not been plugged in, and the reverb setting is always at zero.
...
 Yes. However, it occurred to me at some point a while back that maybe the OpAmp was to blame. So, I removed it as well as replacing it with a known good IC4558, and it did not change anything.
...
IC4558:
PIN 4 = -12.45VDC
PIN 8 = +12.45VDC

My idea was that if the voltage across the op amp was too low, it would clip at less input signal, even if the device itself was in perfect condition. For example, if you power an operational amplifier with 9VDC, it will not put out a signal larger than 7-8 Vpp (less?) because signal can't go further than power supply rails, and in op amps it's a little less than that. So, the input signal will be amplified until it hits the power supply rails where it will be clipped off.
Nonetheless, we can assume that the reverb driver is powered properly, and the extra distortion was generated elsewhere, especially that the reverb pot was turned down to zero, so nothing should have been able to sneak into your signal. I'll keep thinking about it, though.

QuoteWhat am I looking for specifically? Voltages? What is the best way to test the diodes in a circuit? Or does it matter that they are in circuit, and will test fine regardless?

First of all, orientation, especially on components that you replaced, especially polarity-sensitive ones. In circuit, most probably you won't be able to test them correctly because they interact with each other.
First, however, I would do voltage tests around the power supply, points marked A, B, C, and D on the schematic (although C and D seem fine, judging from your op amp test).
For some reason your negative rail (point B) is positive and I'm trying to wrap my head around it. What about the positive rail (point A)?

Maybe test ground connections too?

QuoteAlso, I did replace the rectifier (see attached photo) with one of a higher amperage rating at one point a while back. I don't think this would have anything to do with what's going on, or am I wrong? It should be no different than the one that was in there, except it'll handle more current.

Yeah, a beefier rectifier will do no harm. It's like installing a drain pipe of a larger diameter, it's going to do the same job, but it will be able to take more water. Unless it's dud of course, but yours probably is fine.

Quote from: RG100ESROX on December 09, 2024, 07:41:03 PMThat black wire connects the + side of the left filter can, and - side of the right filter can to ground. (see attached photos)

Thank you. So, that's a ground lug there, underneath the black wire going to the pilot lamp? Yes; it is. Make sure it makes good contact with the chassis.

Where is the transformer center tap connected?

I'll check. Thanks for all of your help and input. It's most appreciated.

I'll try and find the post where g1 requested the voltages of the 'A' through 'E' points on the schematic. I will double check them again to see if they remain the same as previously posted.

M.

Quote from: Miyagi_83 on December 09, 2024, 05:59:12 PMDisregard the pink arrows. I just couldn't find a pic without them. Sorry.

Where does the wire marked with the green arrow go? I can't see it clearly in this picture.

That black wire connects the + side of the left filter can, and - side of the right filter can to ground. (see attached photos)
 

Quote from: Miyagi_83 on December 09, 2024, 05:32:35 PMJay, regarding your preamp settings for the distortion demo

Quote from: RG100ESROXPreamp settings were: P10-B0-M0-T10 (and pulled for clipping)-V3~4-G10

How did you have reverb set? The RCA connectors for the reverb have not been plugged in, and the reverb setting is always at zero.
I'm just thinking out loud now, BUT... Good. I like the idea.

If there is something wrong with the power amplifier's power supply (negative rail measures positive now, according to the image you attached earlier), there might have been a fault in the reverb driver's supply which caused a voltage drop across the op amp, which in turn led to clipping in the op amp itself, which was then blended with the signal. Does that make sense? Yes. However, it occurred to me at some point a while back that maybe the OpAmp was to blame. So, I removed it as well as replacing it with a known good IC4558, and it did not change anything.
Could you measure the voltage at pins 4 & 8 of the 1458? Sure. Last time I did. The voltages were as spec'd on the data sheet for it. I'll check em again just be sure they're still to spec.
And be sure to examine the power supply: rectifier, filter caps, Zener diodes and so on.
M. What am I looking for specifically? Voltages? What is the best way to test the diodes in a circuit? Or does it matter that they are in circuit, and will test fine regardless?

Also, I did replace the rectifier (see attached photo) with one of a higher amperage rating at one point a while back. I don't think this would have anything to do with what's going on, or am I wrong? It should be no different than the one that was in there, except it'll handle more current.

IC4558:
PIN 4 = -12.45VDC
PIN 8 = +12.45VDC

Quote from: g1 on December 08, 2024, 04:49:00 PMWe had established that the trim pot is not located as shown in the schematic.  Then you turned around and said that it was, after all.
But following the traces in your pictures, it is not.  That is why the voltages do not follow.
And if you mark down the voltages on the bias string, it makes it clear that the schematic shows it in a different location.
So why don't you go ahead and record those bias string voltages again, to settle the issue.
Both sides of D7,D8,trim pot,R48,R49.

Before I broke the amp. I had -.6V where it now shows +.524V. Which to me would imply that the component  succession was as indicated on the schematic. The weird thing is... I do have -.6V where the .001uF cap and the collector of Q12 come together. Which makes absolutely no sense at all.

Now, if at one point I did have -.6V where it shows on the trim pot. Would you agree that the schematic was correct?? It's only since I broke the amp that the -.6V no longer exists at that point on the schematic.

What component(s) could possibly make the original -.6V go positive 180 degrees to +.524V???