Hi all,
I'll put some history of the amp at the bottom if you want to read that, or if it may be helpful.
I have recently fixed my dads old Dual Turntable from 1991 and I paired it up with a Sony TA-F170 amp which he used and some old mission speakers from a similar time. currently the amp works most of the time on the right channels but the left channels cut out / fade away to just a crackly noise after a very short amount of time. I have it wired with the high frequencies on the A channels and the low frequency on the B channels for each speakers so they both have two separate inputs. I am almost certain it is the amp not the speakers because if I bob the floating deck of the turntable up and down then the left speaker sometimes kicks in for a short amount of time which is I assume because it forces a surge of current because the needle has a pressure change. And I have heard both speakers play at high quality for a bit together, but it never lasts long. I also tried them with a different input (aux) and the left speaker again doesn't quite work. I have taken the amp apart to see if there is anything obviously wrong, but apart from some very slightly dodgy looking solder joints on the bottom and some brownish what looks like water but it doesn't come of and is not wet. I assume its some small corrosion but it could be a glue of some sort. Also, I don't use it with headphones so it doesn't really matter, but either the port is broken or my headphones aren't compatible. If I wiggle the speaker channel change switch, the speakers sometimes sort of cut out a little, so I think those contacts need cleaning. Sadly I don't have any contact cleaner because I am new to this sort of thing.
If there is anything you think I can do to fix this could you tell me?
sorry if this is in the wrong thread.
History:
This amp was used a lot through my dads university age and was stored in an outdoor shed when he stopped using it. Not temperature regulated but dry. Then my brother found it and used it with a radio in a different shed, still dry, but it was out and being used and not in a box at this time. I think it worked well at this point. Then he brought it inside and used it in his room. Then a couple of years ago he said there was something wrong with it and put it back in its box in the shed and brought a new cheap amp. I recently found it to use with the record player which I fixed and it sort of worked, but I see why he brought a new one. I don't want to buy a new cheap amp, because I've heard this amp work properly and it makes a great sound. At the moment I use it with just the right speaker playing (the left is plugged in it just barely works.) I also like it because it has four outputs instead of two like most amps and it has a pre-amp built in. (and I like how it looks)
Thanks so much for any advice you can give. If there isn't much I can do myself I'll take it to my local repair shop and I can tell them what you tell me to make their lives easier.
Fabian
I'll put some history of the amp at the bottom if you want to read that, or if it may be helpful.
I have recently fixed my dads old Dual Turntable from 1991 and I paired it up with a Sony TA-F170 amp which he used and some old mission speakers from a similar time. currently the amp works most of the time on the right channels but the left channels cut out / fade away to just a crackly noise after a very short amount of time. I have it wired with the high frequencies on the A channels and the low frequency on the B channels for each speakers so they both have two separate inputs. I am almost certain it is the amp not the speakers because if I bob the floating deck of the turntable up and down then the left speaker sometimes kicks in for a short amount of time which is I assume because it forces a surge of current because the needle has a pressure change. And I have heard both speakers play at high quality for a bit together, but it never lasts long. I also tried them with a different input (aux) and the left speaker again doesn't quite work. I have taken the amp apart to see if there is anything obviously wrong, but apart from some very slightly dodgy looking solder joints on the bottom and some brownish what looks like water but it doesn't come of and is not wet. I assume its some small corrosion but it could be a glue of some sort. Also, I don't use it with headphones so it doesn't really matter, but either the port is broken or my headphones aren't compatible. If I wiggle the speaker channel change switch, the speakers sometimes sort of cut out a little, so I think those contacts need cleaning. Sadly I don't have any contact cleaner because I am new to this sort of thing.
If there is anything you think I can do to fix this could you tell me?
sorry if this is in the wrong thread.
History:
This amp was used a lot through my dads university age and was stored in an outdoor shed when he stopped using it. Not temperature regulated but dry. Then my brother found it and used it with a radio in a different shed, still dry, but it was out and being used and not in a box at this time. I think it worked well at this point. Then he brought it inside and used it in his room. Then a couple of years ago he said there was something wrong with it and put it back in its box in the shed and brought a new cheap amp. I recently found it to use with the record player which I fixed and it sort of worked, but I see why he brought a new one. I don't want to buy a new cheap amp, because I've heard this amp work properly and it makes a great sound. At the moment I use it with just the right speaker playing (the left is plugged in it just barely works.) I also like it because it has four outputs instead of two like most amps and it has a pre-amp built in. (and I like how it looks)
Thanks so much for any advice you can give. If there isn't much I can do myself I'll take it to my local repair shop and I can tell them what you tell me to make their lives easier.
Fabian
This is a pretty simple design- Your two biggest gremlins in this type of amp will be dirty contacts and bad solder joints. You will have to get some contact cleaner, (I have used WD-40 in a pinch, but not on amps you really care about.) and focus on the speaker select and source select switches. For the bad soldering joints (look for cracks around pins in really thin joints) you will have to touch up with a soldering iron and fresh solder, or find a friend who can. It does not look like they used the typical brown glue at the base of the electrolytic capacitors, so the brown stuff you refer to must be the soldering resin on the solder side of the board left over from soldering the leads on the big transistors. That's normal. Those leads were hand soldered which is why there is resin.
Since this amp was your Pop's, there is family sentimental value, so unless you feel really comfortable with soldering and cleaner (Which it sounds like you are not) I would take it to the shop. Best have it done properly, and they can take care of any other problems it might be having to ensure a long enjoyable life.
Good on you for wanting to save the good stuff, and keep it alive in the family.
Since this amp was your Pop's, there is family sentimental value, so unless you feel really comfortable with soldering and cleaner (Which it sounds like you are not) I would take it to the shop. Best have it done properly, and they can take care of any other problems it might be having to ensure a long enjoyable life.
Good on you for wanting to save the good stuff, and keep it alive in the family.
Service manual and schematics is available at Elektrotanya.
Looking at it - the first thing to do would be to "work" the source direct switch. In both positions the signal passes through it and such switches may get very oxidized during the years (they are very rarely used and so do not get any internal abrasive cleaning from contacts move).
Some photos of the internals would also be of help.
Looking at it - the first thing to do would be to "work" the source direct switch. In both positions the signal passes through it and such switches may get very oxidized during the years (they are very rarely used and so do not get any internal abrasive cleaning from contacts move).
Some photos of the internals would also be of help.
Thanks for both of your replies, I have done more working of the switches, and it turns out the source selector switch has bad contacts not the speaker selector. I have also worked the source direct button, but it moves very smoothly and seems to be fine. The amp is working great at the moment but the source selector switch has to be in a very specific position for it to work so contact cleaner is on order and then it should be fine. Thank you both for the advice!
I suspect the source selector switch is probably a remote slide switch, e.g., rotary control on the front panel activating a metal slide to the actual switch on the pcb - if so, the slide switch will almost certainly need complete removal from the pcb, followed by switch dismantling, to clean it properly (carefully - they are unobtainable today except from donor units). The slide switch construction is such that contact cleaners, even sprayed in, will not reach the actual contacts properly without dismantling.