Aiwa AX7600 vr problems

[humphrey]

Just got this tuner amp off a mate and want to repair it. I found a relay that needed reflowing and it worked ok but there was noise on the balance and volume pots. They were made by Alps. The balance has two sections with 3 terminals each. part number 24866170 50k ohm
The Volume control is part number 24896160 100k with two sections 4 tterminals each.
Any suggestions for replacements?

[vidjoman]

A good squirt of Servisol will probably get them working properly.

[humphrey]

Now I have the board out, I would like to try something more permanent but I might try your suggestion if I can't find replacements.

[Diabolical Artificer]

Highly unlikely to find replacements unless you get custom pots made by Blore Edwards, a squirt or if that fails dismantle and clean and they should be fine.

Andy.

[Herald1360]

If they're used as board mounts it gets a bit more difficult to replace with anything but identical parts. In any case, the four terminal volume (loudness) pots might have to become simple three terminal volume controls.

You could find smaller pots with the same bushing and fabricate brackets from steel or brass shim to mount them to the PCB with the bushings in the same relative positions to the board and free wire the connections....

Depends on what you're up for I guess.

[humphrey]

I found the identical 4 pin one on ebay but still looking for the 50 Ko-N Would that be linear? Also, how does a 4 pin vr work and can it be used instead? I tried looking for a double pot 50k and while they have 6 pins, don't look similar.

[Herald1360]

The fourth pin goes to a fixed tap on the resistive track and will be connected into some sort of RC network. The effect in operation is that bass is boosted at lower volume levels which is supposed to compensate for the ear's response at low sound levels.

[humphrey]

Would this one work as it has a centre detent for the balance?
https://www.ebay.co.uk/itm/ALPS-RK27...QAAOxy~dNTIj7Z

[Herald1360]

That's seriously expensive! It might just make sense if it were a drop in fit, but otherwise.....

[vidjoman]

Those pots rarely fail completely unless there is a problem with leaky caps putting DC voltage on them. It's pointless to replace unless you can confirm that it has broken. They are easy to clean and that is most likely all that is needed. Mostly due to lack of use over time and slight tarnishing has set in. Don't waste your money on a replacement until you try cleaning etc.

[humphrey]

I can only find larger versions of the originals, so may have to fix them sideways and wire then to the pcb. Does it make much difference if they are lin or log?

['LIVEWIRE?']

Generally speaking, Volume controls are Log (Logarithmic), Tone and Balance Controls are Linear. On Japanese pots the 'law' (Log. or Lin.) is usually indicated by an 'A' or 'B' after the resistance value, but I admit I can't remember which is which. However, as vidjoman says, the pots seldom need replacing, as cleaning restores normal, quiet, operation in 95% of cases. A squirt of servisol (or deoxit) into the body of the pot. is usually all it needs to quieten most noisy controls.

[humphrey]

I would rather change them as it is a difficult access but willing to try cleaning. I really need to test them before re installing. Any ideas for a testing circuit so I can check them individually? I have a Telequip Serviscope minor if it helps.

[vidjoman]

If you were to find suitable replacements - they would probably be 'old stock' and may well be as old as you have already in the player. They could be just as tarnished and noisy when rotated and still need cleaning with Servisol.
You already have a testing circuit - it's the player.

[humphrey]

Agreed, but putting it back to test it will take a long time due to the number of plugs coming off the board.

[vidjoman]

On the only internal picture I can find it looks easy to give a squirt Servisol or similar into the controls without taking it apart.
I don’t think you will be able to mount any other control ‘sideways’ as it’s the controls that hold the circuit board in place.

You seem to have created a mountain of work to do what would normally be a 10 minute job.

[humphrey]

Ok then, I will give it a squirt and see what happens. It aint going anywhere at the moment and parts are hard to find. I have a can of Loctite 7039 which I suppose is the sme stuff.

[Silvered_Mica]

Originally Posted by humphrey

I would rather change them as it is a difficult access but willing to try cleaning. I really need to test them before re installing. Any ideas for a testing circuit so I can check them individually? I have a Telequip Serviscope minor if it helps.

I normally use my analogue Avo 8 multimeter for testing pots, the needle should move nice and smooth up and down without any erratic movement.
Also check the rivets that hold the pins, these sometimes get a bit lose and when this happens I just give them a little pinch with long nose pliers.

I would agree with other post here it's not necessary to change out this type of pot as they are very serviceable unless you have one with a cracked track then it will need changing.

[humphrey]

I sprayed the pots liberally and am pleased to report that there is no trace of crackle though there is some hum on the full volume. Thanks for steering me in the right direction. I could find no schematics anywhere and next time I will make sure that all plugs and sockets are marked with a proper pen and one that does not have ink that rubs off. Thanks again.