October 18, 2021, 03:01:12 AM

News:

Welcome to week4paug.net 2.1 - same as it ever was! Most features have been restored, but please keep us posted on ANY issues you may be having HERE:  https://week4paug.net/index.php/topic,23937


Vintage Audio Repair

Started by nab, September 16, 2021, 06:36:09 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

nab

Quote from: rowjimmy on September 24, 2021, 05:33:19 AMSimilarly, I've got my first electric guitar which is a real piece... I'm going to test out some fancier work on it (split coils) for practice.

Sounds like a good start.

I've got another "final exam/possible entrance to grad school" type project that is guitar related; a Sears Silvertone Model 1484 Twin Twelve tube amp. Can't decide whether to sell it as is or take the plunge. It was handed down to me, so I have nothing in it other than sentimental value and can wait all day, but since I don't really play, I keep getting the nagging urge to move it on to someone who will appreciate it.

nab

Starting to get serious here. I've spent the last few months gathering materials, tools, and in town contacts.

My first serious victim is this Marantz SR1000.

Patient Symptoms: Smoke emanates from power supply board 3-4 mins after start up.
Initial Diagnosis: Diode Q808 is shorted.
Current Treatment Plan: Replace Q808, Q801=805 (which test out ok, but look crispy), and re-cap the power supply board.
Possible Complications: The STK 463 chip is busted and the same problem returns. Initial testing indicates it's ok.   

Got an oscilliscope and variac coming in the mail next week to take the deep dive.

rowjimmy

Getting serious indeed.

nab

Quote from: rowjimmy on October 01, 2021, 10:06:59 AMGetting serious indeed.

Finally found my own hole in the market that intersects with my interests and talents. Here's to hoping it can be solvent enough to at least make my music addiction income neutral.

That's the hope anyway.

Either way, I'll make my addiction less expensive if I can pick up gear that's broken and fix it myself.

But I also think it's real fucking fun. So there's that.   

jam>

Quote from: nab on October 01, 2021, 02:51:58 PM
Quote from: rowjimmy on October 01, 2021, 10:06:59 AMGetting serious indeed.

Finally found my own hole in the market that intersects with my interests and talents. Here's to hoping it can be solvent enough to at least make my music addiction income neutral.

That's the hope anyway.

Either way, I'll make my addiction less expensive if I can pick up gear that's broken and fix it myself.

But I also think it's real fucking fun. So there's that.   

That's awesome!

nab

Well, started up the Marantz SR1000 today again. My variac came in the mail yesterday, so I was able to bring up the power slowly and get it just to the point it starts smoking, without pushing it any more than I had to. Once I got to about 90 volts and let it sit for a couple of mins, I started noticing the smoke, but it's so faint and far above the board, I can't pinpoint it's exact location other than the power board.

Took a picture of the power board and the damage to Q807 and Q808 are worse than I can see with my eyes, readers, and magnifying lens. Both of them will definitely be replaced. They are the diodes circled in the photo. While I'm in there, I'm going to replace the filter capacitors and other electrolytics on this side of the board, especially those in the caustic glue. I have a mess of capacitors coming this week, and will test them as I pull them, but I'm betting they will be showing their age. They're marked with stars in the photo.

Then I'm cleaning the glue that caused this whole mess off the board.

Now to wait on the mail this week.

 

rowjimmy


jam>

I'm diggin this thread. Thanks for play-by-play.

Buffalo Budd

Quote from: jam> on October 04, 2021, 06:45:14 AMI'm diggin this thread. Thanks for play-by-play.
Totally. Thanks for letting us follow along nab.  :beers:
Everything is connected, because it's all being created by this one consciousness. And we are tiny reflections of the mind that is creating the universe.

emay


Quote
QuoteI'm diggin this thread. Thanks for play-by-play.
Totally. Thanks for letting us follow along nab.  :beers:
same. very educational. 

nab

Marantz repair is on hold while I wait for more parts. One of the most frustrating things about doing this from where I'm at is that not having the right resistor can throw you off a week while you wait for more parts. I've ordered several kits of capacitors, resistors, diodes, LEDs, etc., but something exotic pops up.

Unfortunately, I don't have a picture of the progress right now as I forgot to take one before closing up the case to move some other things on to the bench. I've had to make way for three receivers in a row from the local record store. They were all cheap units from the early 80s that weren't worth the money to rehab. I've started desoldering them for more practice and spare parts like RCA connectors, knobs, switches, etc.

The latest victim was a Sony STR-VX1. This unit was produced in the early 80s and was plagued with the same Filter Capacitor glue as the Marantz, but the glue had eaten this unit up way more than it had in the Marantz. One of the main power rails was green with corrosion. The picture below shows the glue, power rail, board degradation, and components I saw with visible corrosion from the glue (starred). The only remedy would be to replace all of these starred components at least, though it is likely they've set others off.

So, if you're buying a rando unit from this era, pop the top and look for the glue and any corrosion at least.

This Sony didn't smoke and put out music and lit up btw.