Fixing an old amp but cant find potentiometers for it.... - Page 1
Forum section: electronics / repair

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: February 22, 2023, 04:44:46 pm
content: Hi all!So im trying to fix a Technics SU-V300M2 and has some sound issues. My main suspect is the balance potentiometer, the part number is EVJ02QF04G15 but all i get on google for that search is the service manual.....I dont even know if thats a "real" part number or mnufacturer specific, any thoughts?

author: wasedadoc
author_rank: Super Contributor
timestamp: February 22, 2023, 05:57:23 pm
content: Why do you think the balance pot needs to be replaced?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: February 22, 2023, 06:39:04 pm
content: Do you even need a balance pot?You could just take it out of circuit.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: February 22, 2023, 06:54:55 pm
content: Back when I was less than 20 years old, I had a NAD 3020. I quite liked that "NAD" sound.But curious, as I never actually used the tone controls, I found a way to bypass the tone circuitry, though it lost some gain in the process.It no longer had that "NAD' sound, but simply sounded way better, as it didn't now have a "sound" at all.Sometimes less is more.

author: Bud
author_rank: Super Contributor
timestamp: February 22, 2023, 10:23:21 pm
content: Quote from: Lockon Stratos on February 22, 2023, 04:44:46 pmIt is the actual part number. Seems to be a Panasonic part number. G15 is likely the taper code G and resistance value 1e5 (100KOhm). You can use a substitute that physically fits but finding the right taper (G) might be a problem. This document has charts for Panasonic taper codes, G is given on one of the chartshttps://industrial.panasonic.com/cdbs/www-data/pdf/AOK0000/AOK0000PJ1.pdfIt resembles the S curve and perhaps can be substituted with a W taper which may be easier to find.Edit: The G taper appears on two charts, one for pots with a center detent, the other without a detent.

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: February 24, 2023, 05:46:06 pm
content: Quote from: wasedadoc on February 22, 2023, 05:57:23 pmCracking and other sound issues, but turns out its the main volume pot...... Gone down the wrong rabbit hole.Quote from: Bud on February 22, 2023, 10:23:21 pmThanks! Sadly as i said above i suspected the wrong part. The volume pots part number is rrv16b05b15a, so presumable it is also 100k...

author: donlisms
author_rank: Frequent Contributor
timestamp: February 24, 2023, 06:55:43 pm
content: Cleaning, cleaning, cleaning!It would be surprising if the balance pot had been worn out - it's probably only been turned five times in its whole life!

author: james_s
author_rank: Super Contributor
timestamp: February 24, 2023, 08:15:38 pm
content: As of yet I have never had to replace a pot in a piece of audio gear. Almost always they can be revived by blowing out with compressed air and a squirt of Fader Lube or similar product.

author: TimFox
author_rank: Super Contributor
timestamp: February 24, 2023, 08:31:50 pm
content: Quote from: donlisms on February 24, 2023, 06:55:43 pmAlso, if a pot has not been moved at all in years, just rotating it a few times will sometimes clean it.

author: NOON Design
author_rank: Contributor
timestamp: February 26, 2023, 03:38:13 am
content: Can also be the coupling caps to / from the pots going leaky with age. DC will make noise across even a new pot.

author: TheMG
author_rank: Frequent Contributor
timestamp: February 26, 2023, 04:55:59 pm
content: I swear by Deoxit Fader F5. Can't remember the last time I actually had to replace a potentiometer (other than ones that were physically damaged). A little squirt and work the pot a few times, good as new.

author: bigpimp347
author_rank: Newbie
timestamp: February 27, 2023, 06:39:17 pm
content: try these people..they seem to have found everything and are selling a lot of vintage items back to china..!!https://www.ebay.co.uk/sch/i.html?item=255990686757&rt=nc&_trksid=p2047675.m3561.l2562&_ssn=electro-niknaks

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: March 03, 2023, 11:33:24 am
content: Quote from: donlisms on February 24, 2023, 06:55:43 pmMy father is working on it, says he flushed it with wd40..... (yeah doubt it was the best idea)Quote from: NOON Design on February 26, 2023, 03:38:13 amHe inspected the boards but according to him there wasnt any leaking caps....

author: wasedadoc
author_rank: Super Contributor
timestamp: March 03, 2023, 04:06:45 pm
content: Quote from: Lockon Stratos on March 03, 2023, 11:33:24 amWD-40 was a very bad idea.Leaking electrically (ie passing dc) and leaking electrolyte are two completely different types of leaking. The former was meant. Which did your father check?

author: Lockon Stratos
author_rank: Regular Contributor
timestamp: March 05, 2023, 11:28:35 am
content: Quote from: wasedadoc on March 03, 2023, 04:06:45 pmHe visually checked them, as for the wd40 he tried that after soaking the darn thing in contact cleaner didnt do anything. Also as it turns out it isnt the factory original so maybe its just a crappy pot....