Slide potentiometer Rec level tape - UK Vintage Radio Repair and Restoration Discussion Forum

mr.fomt · 23rd Oct 2018, 8:12 pm

I have two slide pots on my cassette deck to control the rec level when recording. Its 20k 45mm slide movement, 65mm between screws, 73mm long pots. One of them has worn out, the coal inside is gone, so its not working. I have only found 10k pots with the correct size. Can I use 10k pots instead of 20k? If I replace both of them. I understand that the slider will go up more quickly in volume when slide it. But can I harm the amplifier?
Its a Telefunken 3022 music center. Should I put a fixed resistor anywhere?

julie_m · 23rd Oct 2018, 11:11 pm

10kΩ pots probably will work just fine. The preamplifier stage driving them probably will not mind working into a lower impedance. In the absolute worst case, if the preamp is seriously short of "oomph", you will get a thin and scratchy sound; but permanent damage is very unlikely to result from running the set like this. For a quick experiment, tack-solder a 22kΩ resistor across the two ends of the still-working pot and listen to see if it makes any difference.

Using a different value potentiometer should not affect how quickly the level goes up. The potential divider effect is still the same; both the resistances above and below the slider will be half what they would be with it in the samep osition on a 20kΩ pot.

mr.fomt · 24th Oct 2018, 8:02 pm

Thanks for the reply! Then I think I can use another value without any problem.
The potentiometers I found with the correct size was linear 10k. The old ones is log potentiometers. Now I only find 50k log pots, 73mm long. Is there any problem going up to 50k? Its more than the double. But red somewhere that resistance doesnt really matter but it could affect the impedance in some way

23rd Oct 2018, 8:12 pm	#1
mr.fomt Retired Dormant Member Join Date: Oct 2018 Location: Örebro, Sweden. Posts: 7	Slide potentiometer Rec level tape I have two slide pots on my cassette deck to control the rec level when recording. Its 20k 45mm slide movement, 65mm between screws, 73mm long pots. One of them has worn out, the coal inside is gone, so its not working. I have only found 10k pots with the correct size. Can I use 10k pots instead of 20k? If I replace both of them. I understand that the slider will go up more quickly in volume when slide it. But can I harm the amplifier? Its a Telefunken 3022 music center. Should I put a fixed resistor anywhere?

23rd Oct 2018, 11:11 pm	#2
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Slide potentiometer Rec level tape 10kΩ pots probably will work just fine. The preamplifier stage driving them probably will not mind working into a lower impedance. In the absolute worst case, if the preamp is seriously short of "oomph", you will get a thin and scratchy sound; but permanent damage is very unlikely to result from running the set like this. For a quick experiment, tack-solder a 22kΩ resistor across the two ends of the still-working pot and listen to see if it makes any difference. Using a different value potentiometer should not affect how quickly the level goes up. The potential divider effect is still the same; both the resistances above and below the slider will be half what they would be with it in the samep osition on a 20kΩ pot. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

24th Oct 2018, 8:02 pm	#3
mr.fomt Retired Dormant Member Join Date: Oct 2018 Location: Örebro, Sweden. Posts: 7	Re: Slide potentiometer Rec level tape Thanks for the reply! Then I think I can use another value without any problem. The potentiometers I found with the correct size was linear 10k. The old ones is log potentiometers. Now I only find 50k log pots, 73mm long. Is there any problem going up to 50k? Its more than the double. But red somewhere that resistance doesnt really matter but it could affect the impedance in some way