Pioneer amplifier A-205 Relay not clicking after a mistake i made

[GraphicMan]

Hello guys
Because the unit is old (but only occasionally used) the loudness button causes some noise due to bad contact,
sprays did not work, so i decided to solder the pins that it connects on the pcb at the on (loudness on) position
i did that and it worked fine, i know from the bottom of my heart that the switch connects 2 pins and also d/c other 2 pins
on every position it have (6 pin switch), so i was curious what would happen if i clicked the switch off while the pins are soldered at on (so basiclly on and off at the same time), when i did so the sound is gone, nothing blew
all lights are on normally, except that the unit does not click its relay anymore and ofcourse no sound
the loudness led is not responding also
where the problem could be?
hope to find help here
thanks in advance

[GraphicMan]

again my bad, i was not connecting the prob properly, too afraid to short next to the gnd pin
the +15 is there very exact
thank you again for the much better pdf, that helps a lot (assuming it is the same schematics)
i really did notice way deeper BASS! after that repair, coz i also did disassemble the pot , it was so scratchy , i even needed to mill a small copper ring with a stick (0.1mm thick) and placed it on the inner carbon resistant ring, the outer was not worn out, so the inner of the left channel was causing the issues, no the loudness switch is much better, the direct which is so big switch is very scratchy , i need to disassemble and clean it, but these switches are really hard to assemble , it is very very complex and delicate, if it gone perhaps the whole amp wont work again, and wont even know what it does to try to replace it
you guys are really good at what u do, thank you very much for your patience and help, u r a life saver

[R_J]

You should not have done that, you likely damaged either the +15 or -15 volt supply, I would suspect the +15 volts is bad, One side of the dpdt switch controls the led so connecting its pins shorted out the led, the other side of the dpdt switch shorted the -15 and the +15 together

[redwire]

I can't make sense out of what was done. A205 uses JFET switches for the loudness mode, 1/2 the DPDT switch is for the LED.
But likely shorted the +/-15V rails causing the end. Resistors 4.7R should have fused at the Vreg inputs.
cross-posted: https://forum.allaboutcircuits.com/t...-i-made.200661

[GraphicMan]

correction, the LED all working fine, i thought it was bad but the direct switch was on , so that automatically disables the loudness switch all together along with its led
so again the leds are ok
do u still think that the +/- 15v is gone?
plz let me know where i should test for that
i really wish some1 helps me out
i did test many transistors on 2 boards and nothing that i found bad
the problem is that the online service manual is not helpful due to a bad scan
so i really wish for help here
thanks in advance

[GraphicMan]

you are both correct
i just tested for the +/-15 volts, the -15 is there, the +15v is not there (zero)
i tested at that white connector
thanks
what next?

[redwire]

There are two +15V regulators. One is for the LEDs.
Check Q321 and R367 is 4.7R fusible, probably blown.

[GraphicMan]

the Q321 was giving me some readings when tested on board, but one reading was suspicions so i thought i pull it out and test it, it looks like it is using old school base collector emmiter, the base was not in the middle, according to that it is testing ok 0.615 voltage drop on both E and C and nothing in reverse , also nothing between C and E, i am assuming it is good
i did not find R367 , just 367 and it actually giving me 34 vDC ! probably some caps are still charged, it is also giving me continuity, attached close up pics for the pcb, what do u think boss?

[GraphicMan]

Here is another high quality large pic for the whole pcb, hope that helps

[CapLeaker]

Here is another high quality large pic for the whole pcb, hope that helps

I see many cracked (rings) solder joints that need to be fixed.

[redwire]

Look at these resistors on the other side. I think R368 is 4.7Ω 1/4W fusible and is open, so the -15V rail would be gone.

[GraphicMan]

Look at these resistors on the other side. I think R368 is 4.7Ω 1/4W fusible and is open, so the -15V rail would be gone.

R368 = read 8.8 ohms
R367 when positive lead is on left, negative on right = short, when flipped the leads = open
shall i pull it out and test out?
many thanks for ur help

[GraphicMan]

I see many cracked (rings) solder joints that need to be fixed.

not as bad as it look but i can reflow all that once i get to the fault

[GraphicMan]

Look at these resistors on the other side. I think R368 is 4.7Ω 1/4W fusible and is open, so the -15V rail would be gone.

btw the +15v is the missing, -15v is there as mentioned before

[GraphicMan]

Look at these resistors on the other side. I think R368 is 4.7Ω 1/4W fusible and is open, so the -15V rail would be gone.

yeah man i got the 367 out and it is giving me mega ohms!
shall i just replace it and test or there might be other issues?
thank u so much, u r really good

[CapLeaker]

Lift a leg on both of the resistors and take an ohms reading. A 4.7ohm resistor reading 8.8 ohms is out of spec! A 4.7ohm resistor reading mega ohms is basically open. So both need replacing if that's the case.
A component is best tested out if circuit.

[GraphicMan]

Lift a leg on both of the resistors and take an ohms reading. A 4.7ohm resistor reading 8.8 ohms is out of spec! A 4.7ohm resistor reading mega ohms is basically open. So both need replacing if that's the case.
A component is best tested out if circuit.

agreed , i will also measure the one giving me 8.8 ohms and let u know
how did u guys know the original value without seeing the color code which i did see and it is gold gold , violet and yellow (4.7 ohms)
i could not find it even on the service manual
another question, what if i did not find that fusible resistors, what can i use as a replacement?
thanks

[GraphicMan]

i got it out and it is 8.6 ohms using 2 DMM, it has the same color code as its sister , should be 4.7 ohms,
now what?

[CapLeaker]

agreed , i will also measure the one giving me 8.8 ohms and let u know
how did u guys know the original value without seeing the color code which i did see and it is gold gold , violet and yellow (4.7 ohms)
i could not find it even on the service manual
another question, what if i did not find that fusible resistors, what can i use as a replacement?
thanks

The value of the resistor is in the manual. You just need to know how to read it. R367 & R368 RD1/8mmf4r7j is on the bottom of page 19 in the service manual. 4R7 = 4.7 Ohms. Plus it has to be a low ohms resistor in that location. So 4.7 Ohms sounds about right and it isn't an odd value resistor either. The RD1/8 is the wattage, so this is a pretty small resistor like the small ones in your post #5. The resistor is fusible because, if you bridge the connection instead of using the resistor, probably you burn up more chit you'd like to hear.

"i got it out and it is 8.6 ohms using 2 DMM, it has the same color code as its sister , should be 4.7 ohms,
now what?"

Now you need to find two replacement 4.7Ohm resistors 1/8 watt and replace it. Now if you lucky the +15v should be on one side of the resistor still there, it just didn't pass through because the resistor was basically open. If you are not lucky the +15V regulator failed and it needs to be replaced as well.

[R_J]

Short your meter probes together in resistance mode, you are likely measuring a couple ohms of lead resistance when checking R368 (4.7Ω). The values are marked on the schematic,I would just replace both 4.7Ω resistors

[GraphicMan]

Short your meter probes together in resistance mode, you are likely measuring a couple ohms of lead resistance when checking R368 (4.7Ω). The values are marked on the schematic,I would just replace both 4.7Ω resistors

shorting the leads gave me 0.4 ~ 0.5 ohms, so it looks like the resistor is off, the unit is about 24 years old but rarely used
i have already tested q321 outside the pcb and it is good (is not that the regulator u mean?)
if the the regulator is gone then the resistors cant be a fusible i think, however the resistors really look like normal ones, they dont have the extra while band, what kind of amps should it blow at, i can make a test on the semi good one and see when it will fail with my volt station? i also need to know how to determine them fusible or not when i buy them to make sure, i looked that up and could not find an answer, plz let me know

attached page 19 from the service manual i have, it is terrible pdf, can u share the one you are looking at? i could not find any other better version, it is the only available one
thanks guys so much