SPEC-1, Lower output on the right channel

[ajohnnyz]

So I have tracked it down, now what to do?

Here are a couple pictures. signal going in Aux1, Aux2, Tape, etc., all the same, that's not the issue. Signal coming out of the Output 1 or 2 both low on the Right channel. I don't know if there are any VR's that can correct this? Front Balance has to be on 2 o’clock to be balanced.

FYI, I cleaned all switches very good.

The only VR's I can see are on the power supply, I don't see any info on how to set them? I don't see any other VR's to balance this?

If any one has some ideas on where to start and what to look at I would appreciate it very much.

 

[kwayde]

Since you have a scope you can check your signal at the inputs and outputs of each board in the chain to see where it drops lower. Skip the EQ board as the signal isn't going through that one.

 

[ajohnnyz]

Since you have a scope you can check your signal at the inputs and outputs of each board in the chain to see where it drops lower. Skip the EQ board as the signal isn't going through that one.

View attachment 2535659

Thank you for getting back to me. Just a little history I just started doing this 3 months ago. I am a fast learner, There has been nothing in my life that I cant do, this has been on my bucket list and I am learning. I have tried to keep up on all the tools,... I can learn and do all you ask I am a sharp guy, but at this point of my leaning I have know idea what you want me to do. Sorry, please help me help you. sorry... I am very happy to learn alilI can do with the signal generator and scope.

"check your signal at the inputs and outputs of each board in the chain to see where it drops lower" ?

 

[kwayde]

I'm using the schematic in the service manual from https://elektrotanya.com/pioneer_spec-1.pdf/download.html#dl

On page 28 is the schematic. It shows the signal paths for the left and right channels through the amp. It shows the pin numbers on the boards where the signals go in and come out on each board. Using the block diagram I sent in post #2 you can see which boards the signals travel through. Using the schematic, look for the input pins and output pins to check if the signal drops on the right channel.

If the signals are equal going into the Tone board at pin 1 (L), and pin 22 (R), then you know things are good coming from Aux. 1 assuming your signal in is hooked up to that input. Then check that board at the outputs, pin 10 (L) and pin 13 (R) If the signals are good, then move to the next board following the schematic. This schematic is nice that it has arrows showing signal ins and outs. By checking these you should come across a drop in signal strength somewhere which will narrow down the area of concern.

 

[kwayde]

I don't know how familiar you are with reading schematics, but this one shows the switch positions on the right hand side, along with other pertinent information. Each board is outlined with a dash-dot-dash boarder. Each board is labeled above showing which is which, plus it shows the board number. Each board is shown in the manual in detail so you know exactly where the parts, pins, etc. are.

 

[mikiekimi]

Do the channels even out with more volume? What volume was it set at when you had it on the scope?

The volume step attenuator is a different beast and is a PITA to clean, but if it’s dirty you may see diminished output on one channel. I serviced one a few months back that was weak on one channel until I hit a certain point on the dial, then it evened out. I disassembled and cleaned the volume control and it was resolved.

If you toggle the attenuator to -15 or -30 does the volume issue change?

 

[markthefixer]

No, there aren't any other VR's to balance it...

these interactions are all on the front panel, use your existing cabling configuration, and are quick:

turn on and off the tone switch - no change in the difference between the channels?

turn on (15Hz and 30 Hz) and off the low filter switch - no change in the difference between the channels?

turn on (8KHz and 12KHz) and off the high filter switch - no change in the difference between the channels?

turn on (-15db and -30db) and off the attenuator switch - no change in the difference between the channels?

I'm gonna call the traces PINK and YELLOW, OK? PINK is bigger than YELLOW.

annnnd.... the money shot:
the mode switch:
---------------------------what does this mean - has the damage to the signal has already happened BEFORE the mode switch? ------------------------------------------------------------

reverse...............YELLOW is bigger than PINK
normal.................PINK is bigger than YELLOW.
mono L + R........ PINK and YELLOW same size large
mono L ...............PINK and YELLOW same size large
mono R.............. PINK and YELLOW same size small

----------------------------------------OR ----------------------------
IF PINK is ALWAYS bigger than YELLOW.
then
the damage to the signal happens AFTER the mode switch.

I was looking to find and point at a few good spots in it to check levels as they jumped from board to board. It wasn't that long ago that I had one open on the bench, it's still around but the volume control is disconnected - part of that (interrupted)Spec-1 replacement volume control project.

 

[markthefixer]

If you can post 2 pictures, one of the bottom of the unit - there will be a lot of probe points there
and one of the top of the unit, concentrating on the AWG-035 tone board.

There's just 4 probe points on the tone board, but it's the top of the board
and I don't remember what there is up there to grab a scope probe onto.

IF the signals are messed up at the first probe points AWM-082 pins 28 & 30, then the mixing relay on the mixing board has dirty contacts.
The mixing board also has the balance pot,

I have probe point PAIRS for your scope mapped out.

 

[ajohnnyz]

Do the channels even out with more volume? What volume was it set at when you had it on the scope?

The volume step attenuator is a different beast and is a PITA to clean, but if it’s dirty you may see diminished output on one channel. I serviced one a few months back that was weak on one channel until I hit a certain point on the dial, then it evened out. I disassembled and cleaned the volume control and it was resolved.

If you toggle the attenuator to -15 or -30 does the volume issue change?

No it doesn't even out. The difference is consistent with all volumes. I worked the volume knob very good and it seams to be in very good shape. No static or changes at all.

 

[ajohnnyz]

No, there aren't any other VR's to balance it...

these interactions are all on the front panel, use your existing cabling configuration, and are quick:

turn on and off the tone switch - no change in the difference between the channels?

turn on (15Hz and 30 Hz) and off the low filter switch - no change in the difference between the channels?

turn on (8KHz and 12KHz) and off the high filter switch - no change in the difference between the channels?

turn on (-15db and -30db) and off the attenuator switch - no change in the difference between the channels?

I'm gonna call the traces PINK and YELLOW, OK? PINK is bigger than YELLOW.

annnnd.... the money shot:
the mode switch:
---------------------------what does this mean - has the damage to the signal has already happened BEFORE the mode switch? ------------------------------------------------------------

reverse...............YELLOW is bigger than PINK
normal.................PINK is bigger than YELLOW.
mono L + R........ PINK and YELLOW same size large
mono L ...............PINK and YELLOW same size large
mono R.............. PINK and YELLOW same size small

----------------------------------------OR ----------------------------
IF PINK is ALWAYS bigger than YELLOW.
then
the damage to the signal happens AFTER the mode switch.

I was looking to find and point at a few good spots in it to check levels as they jumped from board to board. It wasn't that long ago that I had one open on the bench, it's still around but the volume control is disconnected - part of that (interrupted)Spec-1 replacement volume control project.

 

[ajohnnyz]

1. The signal remains consistently different while changing and using every switch other then the balance knob.
2. I added pictures of top and bottom.

3 test points:
Pins 28 and 30 signal is good (even), 26 and 27 signal is good (even)
Pins 31 and 32 signal is good (even) PINS 20 and 22 SIGNAL HAS THE CHANGE IN IT (not even)
Pins 14, 16, 33 and 34 all have the changed signal (not even)

The issue is happening between Pins 31 and 32 and Pins 20 and 22.

 

[markthefixer]

AWM-083 Filter amp assembly, where the switches are low filter (15Hz and 30 Hz) and high filter (8KHz and 12KHz),
four transistors, bunch of caps, two switches. Bottom board in unit.

Both of the filters off exhibit the symptoms. Either filter on does not make a difference in the level imbalance. Correct?

inputs on 31 & 32, outputs on 22 & 20 .

chase the signals left to right on the schematic, there will be a point where the signal on one side of a capacitor will be smaller than the other side of the same component. of course you can also compare left to right channels.

 

[markthefixer]

From your photo:
(sorry I had to crop it in in order for the software to accept it)

 

[ajohnnyz]

Well, it’s not going good at all. I just turned it on to test what you have given me and there was smoke and it blow fuse 12 and 13.

I had the filter amplifier assembly board lose so I could look it over. I looked at it good before I turned it on but I guess not good enough. I put the board bake in place and the screws back in an replace the fuses. Now testing is different. Signal ok on pins 28 and 30 but that's it from there its different.

I think the smoke was coming from the mixing amplifier assembly? I am so upset, kind of sick over it. I am just so mad at myself again.

I honestly couldn't see that the board was hitting anything but maybe pins 14-16 and or 18-22 hit hit the metal frame? I should have put the board back in place, I was going to do that but then I said "no its ok its not hitting anything". well I was so wrong!

I can see an problems visually. And I still don't know what was hitting what. All I know is there was smoke and a very strong sweet smell.

 

[markthefixer]

sigh, tests didn't need loose board. but I didn't say so.

all boards in place?

gotta check power supply, and as you can figure - it takes time to do those graphics.

i'm literally in the middle of something i can't stop.

you need to learn how to read the schematics, power supply awr-094 is right up top. pins 1 - 5 is +48v, 8 - 12 is -48v, 14 & 15 is +24v.

power supply board could be ok. probably not, so we check..

get the dmm black lead to a bare metal chassis ground.

probe with the red probe - insulate all but the tiniest part of the tip as a good practice to avoid shorts when you (we all slip) slip.

after this, no power for a while.

standard drill, loosen the power supply board, test the resistors (ohmmeter) and transistors (Atlas DCA). I'll get parts specified to order.

other resistors in the unit on the power bus may have been damaged, those i'll find later for you to check.( power supply board could be ok, and they shut down circuitry)

when boards are loose, carpet fragments that insulate sides as well are used....

 

[ajohnnyz]

Ok, its not your fault at all. I should have left it all together. I didn't sleep at all last night. I am so upset that I didn’t listen to my inner voice that told me to put the board back in place first. I know better and yet I screwed up, just very upset with myself.

FTI, I saw smoke coming from the Mixing Amplifier Assembly back side of the board had smoke there (see picture) and it smells sweet right there. I cant see the front without pulling out the board out. I had the unit on about 20 seconds when I started seeing smoke . But I don't know how long of that 20 seconds any of pins 14-16 or 18-22 on AWM-082 touched the chassis. But one or more did for sure.

Power Supply Board AWR-094-C
Pins: 1-47.4v, 2-47.4v, 3-47.4v, 4-47.5v, 5-47.5v, 6-55.9v, 7-56.8v, 8-47.6v, 9-47.6v, 10-47.6, 11-47.6v, 12-47.6v, 13-29.6v, 14-23.8v, 15-23.8v

Fuse Board AWX-091-B - there are no volts on the schematic for these pins?
Pins: 1-55.8, 2-0, 3-0, 4-54.8, 5-54.8, 6-28.8, 7-0, 9-1.7, 10-.18, 11-.19, 12-.18, 13-.16, 14.01, 15-0

Also I figured out what the 2 VR's on the AWR-094. VR's set volts at pins 1-5 and 8-12. I dialed in 48v for each. So reading are all a little different now:
Pins: 1-48v, 2-48v, 3-48v, 4-48v, 5-48v,
6-55v, 7-55v,
8-48v, 9-48v, 10-48, 11-48v, 12-48v,
13-29v, 14-24v, 15-24v

Pulled out and tested, probably didn't need too.
Q7 is ok
Q4 is ok
Q6 is ok
R10 10.2
R11 569.8

I soldered all compounds back in. Other then pins 6-55v, and 7-55v, schematic says 62v, I don't know, all seems fine with the Power Supple Board?

And again, I just want to say how much I appreciate you sticking with me through my stupid mistakes. I am not trying to make any excuses but I can say most things I have learned in life was by making mistakes. But at age 57 I have gained a lot of wisdom and I didn’t listen to that wisdom voice and that’s why I am so upset. Plus the SPEC-1 WAS in mint condition. Everything was going so smoothy, your instructions were great and we had it narrowed down and I was on my way to fixing it. I was really enjoying the whole process. The new bench setup, everything was going great, then this! I am trying really hard to think positive at this point.

I tend to use these probes now. I take my time and I am VERY careful.

So here is the scope now AWM-082. Purple Channel is on 31 and Yellow is on 32. Not only is the one channel hardly working at all the working channel is much lower then it was. I am just trying to provide you with all the info I can to help make best use of your time.

And as far as learning schematics, your are right. I am learning. But please keep in mind a few months ago I didn't know what a capacitor, transistor, or diode was. And I had no idea at all how to read a schematic. But thanks to your help I now know what all this is and I am learning the schematics. I couldn't have done any of this without your help.

 

[Young46]

I have these that are good for getting into tight spots. They are about 1 1/2” long and have plastic sleeving covering all but about 3/32” of the tip. Can’t remember where I got them though. I’ll look and post if I find where I got them. I use a mini grabber to ground to the chassis and this one for the probing.

 

[ajohnnyz]

I have these that are good for getting into tight spots. They are about 1 1/2” long and have plastic sleeving covering all but about 3/32” of the tip. Can’t remember where I got them though. I’ll look and post if I find where I got them.

Very Nice, I like them.

 

[ajohnnyz]

Mark, I have been adding to the reply throughout the day. When / if you have time I need help figuring out what to check next. I know your busy, this is not life and death.

 

[markthefixer]

I will say at first glance, you have covered quite a patch of ground here, and covered it well.

I am surprised (and happy) to see the +/- 48v regulated voltage supplies healthy.
pins 6, 7 & 13 are raw dc and quite a range of voltages are acceptable.

Signal sent to unpowered electronics will be hurt in various unpredictable ways.

there are almost no resistors in the power lines (power line filters going into boards) to burn up and interrupt power.
That smell was audio parts...