Any help in fixing a JVC JA-11 Amplifier?

I also have picked up a JVC JA-S11 + MCS 6601 DD TURNTABLE im having the same issues as above and other additional

1. Only phono input is the only input that seems to work and only the Top/Left/White Input (rca female on back)
2. Only left speaker channels work and only outputing left side of the "stereo input"
And regardless of source device i tried the following on all 3 inputs (Aux,phono,tuner)( only the left/top phone worked on all device types) the turntable, a bose radio via audio rcas male to male , and my phone/mp3 player (using a 3.5mm mini jack male to rca pairs red/white male) Again i Also tried each rca connector in each of the input female rcas on back(not tape/rec unsure how that worsks) only left phone worked regardless of source device or right or left rca connector (red or white) so i know its not source devices as i recreated above using a stereo with rca aux inputs and other than the lack of preamp for the tt(super quiet) both channels and all sources worked as they should etc....

3. While playing with knobs on front i get random cuts in and out or it cuts off completely, vvolume, source and the tape buttons seem to be the main culprits here (also the tape button on right side on front was the one i played with and toggled and i had to get it just right in the middle (source ... i dont know how the tape dubbiging stuff is supposed to work nor do i think i wanna or need to use it if someone could explain id appreciate it, or a user manual?)

Basically other than only phono left input and left speaker system 1 output being only able to work when knobs and other stuff is tweeked without opening it yet i assume connection, short, or the controller knob is bad internally, or the same for the inputs on back . I have only peft not right like above posters , i plan on opening and using some air duster and do light cleaning if necessary and check connections soon here but im not sure that will fix my issues? Is this amp a dud? Or dead? Can i fix it? Any info, tips, etc is much appreciated!

Thanks In Advance!

Questions..... just ask reply or pm me

Operate any pushbuttons / input select switches / tape monitor switch / speaker select switch etc. 20 - 30 times each.

It is very common for the switches in older equipment to become tarnished over time and a slight movement or vibration can shift the contacts on to a tarnished area, messing up the functions.

Operating them a number of times often cleans off the tarnish and they work normally again.

So i took the case off and first i noticed one fuse on the board is blown.. i plan to take advice in this thread and clean and air out everything in just once over all visable connectors im hoping its not more than a dust /corrosion and fuse thing

RiddlingCactus said:

Hello! I've been following different threads for fixing the JA-S11G amplifier since i got my hand on one my self! I also had the same problem with only sound from one channel(Right) and as i was trying different things i noticed when i turned the balance all the way to the left i could hear a slight sound coming from the left channel, in my case this had to do with the "Monitor Switch" on the front panel, it has some kind of bad connection so when i worked it slightly up and down the sound would suddenly appear, and suddenly it was gone again. I would also think some of the others switches can have some malfunction/bad connection which causes problem with the output signal to the speaker relay on the back. Either way, this was after i replaced the two Darlington Power Packs(STK-0040, from Ebay) since the 24v- DC relay wouldn't switch over, and that would be the easiest way to try fix it, and it worked!!(shipping costs was over the actual price of the two Darlingtons), and then the next problem was sound coming only on one channel which in my case is the front panel switches, caused by being stored outside summer/winter(i would think?) for over almost 15 years! I hope this helps, it worked for me...

Edit: i used something called "Electronic cleaner", i just unscrewed the front panel, pushed the "clothing piece" aside and then applied some cleaning fluid as i rapidly pushed the switch up/down several times, i did this a couple of times and it's working much better but still the connection sometimes break, it may be possible to mod the switch in someway? With the help from a data sheet/schematic or something, or with the proper knowledge, i am not an engineer but it shouldn't be that big of a problem..

Click to expand...

Exact same problem. Cleaning the monitor switch worked for me also. Thankyou !

for future reference here's the schematic of the STK pack: