Bassblaster
Super Member
alrighty, just placed my order for the new caps. havent got a shipping date yet but im assuming a week
Fisher RS-881A Amp Repair Fail? Has its days come to an end?
- Thread starter Bassblaster
- Start date
Bassblaster
Super Member
Waiting for new caps to arrive.
Bassblaster
Super Member
NEW CAPS ARE IN! now i gotta figure out how to get the board completely out of the chassis
Bassblaster
Super Member
Recap is done, but a problem. i now have a very weak left channel. possible i put a cap in backwards? of maybe even i put the wrong value in somewhere.
i also sanded the LEDs in the front
i also sanded the LEDs in the front
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elnaldo
Lunatic Member
If just one channel is weak, that rule out the power supply.
I'd concentrate in hard to reach places, caps that were dropped while working, a capacitor you placed while the phone was ringing, solder bridge in some place you can't see easily, any point you don't trust 100%.
Be obsessive and compare both channels from the input, following the schematic, value, polarity and soldering of each capacitor. Having one channel working is a good thing, use that to compare.
I'd concentrate in hard to reach places, caps that were dropped while working, a capacitor you placed while the phone was ringing, solder bridge in some place you can't see easily, any point you don't trust 100%.
Be obsessive and compare both channels from the input, following the schematic, value, polarity and soldering of each capacitor. Having one channel working is a good thing, use that to compare.
Bassblaster
Super Member
i triple checked and i have all the right caps in the right spot. my luck i screwed up the trace when i accidently slipped with my Iron. well this will be fun.
Bassblaster
Super Member
checked again, no solder bridges all the caps are in the right way. i have no idea what happened. i still have the right channel but now i dont have a left channel. most likely i accidentally cut through a trace. if that is the case, i might just take a wire and run it from component to component bypassing all of the trace on the left channel. but where would i start is the problem. the part i scratched is in the STK area and i dont know if i hit an input trace or something in the feedback network.
EDIT: Elnaldo and pete since you 2 know a bit more than i do what should i do? i still have that test probe i made back on page 20. im thinking get that probe and test at points until the signal stops
EDIT: Elnaldo and pete since you 2 know a bit more than i do what should i do? i still have that test probe i made back on page 20. im thinking get that probe and test at points until the signal stops
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petehall347
the brandy coffee man
check traces with your meter .
Bassblaster
Super Member
remember my multimeter doesnt read audio signals properly. i edit my last post read on it again
petehall347
the brandy coffee man
i meant measure continuity from point to point .
Bassblaster
Super Member
ok so i measured continuity all the way back to the outputs of the volume control chip to pin 3 and 20 on the STK and i had continuity on both channels there. next idea?
EDIT: i was looking at the board where i slipped and the green coating was a little scratched but it doesnt look deep enough to go completely through the trace. wonder why i completely lost my left output.
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Bassblaster
Super Member
i hope so. if not i have no idea what went wrong where
Bassblaster
Super Member
i tested with headphones and still only sound on the right. now i have to find why i have no left. i might just reflow everything. im going to re flow all the speaker output wires from main board to headphone jack, then from headphone jack to speaker plug board
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elnaldo
Lunatic Member
I recently fixed a mixing console, this morning. The problem was a tiny trace broken right at a capacitor solder pad. Not visible at all. The solder on the capacitor looked OK, The trace too, but there was no continuity between the capacitor lead and the rest of the circuit. When desoldering the capacitor I realized a small ring of copper came off.
So, you need to test continuity or trace the signal with your probe, comparing channels.
So, you need to test continuity or trace the signal with your probe, comparing channels.
petehall347
the brandy coffee man
if you check dc offset you should see if the speakers are connecting or not .. there is near enough always a measurable offset .
then you might want to do that buzz test again like you did ages ago .. just touching the top of the coupling cap should make it buzz somewhat .
then you might want to do that buzz test again like you did ages ago .. just touching the top of the coupling cap should make it buzz somewhat .
Bassblaster
Super Member
i resoldered everything, for offset i have 22.3mV DC on the right and 44.5mV DC on the left. since i resoldered everything is it worth a shot to put some speakers back on and test again?
Bassblaster
Super Member
AY I DID THE BUSS TEST AND I HAVE BUZZ ON THE LEFT! So my problem has to be in the preamp area.
petehall347
the brandy coffee man
that proves the speaker connections back to the amp chip are good then ..yes give it a whirl .
ok my reply was late .. maybe try same with other coupling caps working backwards towards the input .
ok my reply was late .. maybe try same with other coupling caps working backwards towards the input .
Bassblaster
Super Member
Hmm, i dont know what caps to try. lets narrow it down. im missing left output on all inputs. so problem is after that. i believe that leaves the 2 caps on IC302 and balance fader, then a cluster of caps on the EQ bit and IC303 which are wired together.
may be a BIT late for this but i sent my manual to HiFi engine and the person put the board layout and schematic together so it looks way better
http://www.hifiengine.com/manual_library/fisher/rs-881.shtml
