Record Player - Missing Capacitor - Slow To Start - Page 1
Forum section: electronics / repair

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 08:03:48 pm
content: Record player became slow to start - pulled apart and noticed missing capacitor - could not find the capacitor in the chassis to see what it was order one and replace it.Pictures of the layout below. Capacitors around it are 22000pf and 4700pf (I think I've done the "reading" right).I assume the response to this is going to be "it really doesn't matter that much, just pick something like the ones around it" - but I'm definitely no expert on this, so figured I would ask to be sure.I also assume there is a way to calculate the ideal capacitor based on the circuit, but I'm not good at reading what appears to be a more complicated circuit (at least for me). If I get in the ballpark, and it works, I'm good with that.Thank everyone in advance for their help. Appreciate you guys sharing your electronics wisdom.https://photos.app.goo.gl/pVXa4foz7qcJvSoY7https://photos.app.goo.gl/urn8AazU3e33af9f7https://photos.app.goo.gl/4UBQ3mXpW6tdrg4o8

author: abdulbadii
author_rank: Frequent Contributor
timestamp: December 11, 2021, 08:16:39 pm
content: You must have its schematic out of it, in other word try doing RE

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 08:28:23 pm
content: I don't have a schematic. The manual doesn't provide anything, nothing is hidden w/in the record body that I can tell (its a later model - I've seen where earlier ones had basic electronic schematics - this one is a pretty sophisticated one that can be programmed to play tracks in different orders - I think a schematic would be pretty complex).https://drive.google.com/file/d/1hOSuEPnuuXfVN-qj6Ay8GpLQy4Wu_vES/view?usp=sharing

author: james_s
author_rank: Super Contributor
timestamp: December 11, 2021, 08:33:12 pm
content: I'd try something around 10 or 22uF, possibly as high as 47uF and see what happens. Judging by the size and the silkscreen it's an electrolytic capacitor, likely something between 1uF and 100uF, there aren't too many standard values in that range and it's unlikely to hurt anything if you get it wrong.You could also reverse engineer the circuit and with a schematic it might be easier to take an educated guess.

author: fzabkar
author_rank: Super Contributor
timestamp: December 11, 2021, 08:41:48 pm
content: The pinout looks strange. The IC has 6 pins, but I see only 5 on the solder side of the PCB. The datasheet shows 5 pins, but not the same ones. :-?https://datasheet.datasheetarchive.com/originals/scans/Scans-007/Scans-00143996.pdfIn any case, the maximum supply voltage is 25V, so I'm thinking that a 25V capacitor would be good enough. Perhaps 10uF is all you need.That said, I don't believe this will fix the slow start problem.

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 08:44:15 pm
content: Ah - abdulbadii was telling me to reverse engineer "RE" - now I understand.That part of the player is pretty simple - maybe I can figure figure it out - worth a shot. Though fzabkar says it looks strange . . . uh-oh. Maybe not worth a shot :-) If I can't figure it out then I'll just do trial and error.I'll check the recommended resources here for reverse engineering - google revealed some resources as well. I had previously tried a search to see how that was done, but I think my search terms were so off I wasn't getting anything. Now I'm getting stuff that seems like it will help me know enough to give it a shot. Dust off the old EE from 20+ years ago.Thank you to everyone.

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 08:47:07 pm
content: Why don't you think it will fix the slow start problem? The capacitor is on the board that is used to adjust RPM, etc - but that was the extent of my analysis.Any clue what I should be looking for?

author: fzabkar
author_rank: Super Contributor
timestamp: December 11, 2021, 09:04:02 pm
content: The capacitor filters the DC supply to the motor and IC. Since the supply is generated elsewhere, there must be a larger filter capacitor (and diode rectifiers) at another location. If I'm wrong, and there is no other capacitor, then, yes, a missing capacitor could explain your problem. It could also be that the other capacitor has dried out.

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 09:12:21 pm
content: Very interesting - thanks for the assessment. I'll look at it further and let you know how it turns out.

author: m002922
author_rank: Newbie
timestamp: December 11, 2021, 10:18:59 pm
content: I think your assessment was quite astute . . . Appears at least one of the 1000uf 25V capacitors near the power supply is having issues. Probably both. Would have noticed that had I pulled everything apart and looked for obvious things - I sort of found the smaller capacitor in an area that seemed right and quit. Thank you all again for your assistance.https://photos.app.goo.gl/RDNCKDs9B9f1FHqk9

author: m002922
author_rank: Newbie
timestamp: December 21, 2021, 04:51:58 pm
content: I replaced the two suspect capacitors and I am listening to my record player - which now starts right up to full speed without assistance - right now. Didn't even mess with the little capacitor, as I figured it may not have been there in the first place, and seemed to have been working fine without it. So far that dirty assessment seems to be right.First time replacing capacitors. Learned the lesson of the value of a full visual inspection.Thank you all for your help.

author: wraper
author_rank: Unknown
timestamp: December 21, 2021, 04:54:12 pm
content: Quote from: m002922 on December 21, 2021, 04:51:58 pm100% missing capacitor was there since the remains of the broken terminals cannot appear from nowhere.

author: m002922
author_rank: Newbie
timestamp: December 21, 2021, 05:07:40 pm
content: Interesting it didn't turn up when I took it apart . . . but you're probably right. I'll go back in and try the RE and if that fails just put in a standard size and see what happens.

author: james_s
author_rank: Super Contributor
timestamp: December 21, 2021, 09:57:06 pm
content: It's possible it fell through a gap somewhere, or someone may have opened the unit to see what was rattling inside it. Or they may have deliberately removed the capacitor by snipping it off for some unknown reason.