Rockola 474 re-cap amplifier question

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Topic author
Torontotom
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Posts: 6
Joined: Sat Jul 02, 2016 10:55 pm
Location: Canada

Rockola 474 re-cap amplifier question

by Torontotom » Mon Jul 11, 2016 4:56 pm

Making progress on my Rockola, and am now onto (I hope) the final leg. Amplifier re-build. I have done a fair bit of reading and it seems pretty obvious I need to replace the electrolytic capacitors in the amplifier. Basically all I get when I turn it on is a loud hum, and I get no sound from the turntable at all. I have checked continuity on the cartridge lead and that seems to be fine, 99% sure the amp is the problem.

I have included a link to two pictures of the amp. It is broken up into several smaller components.

https://goo.gl/photos/j2vipdVjyutWJJdZA

The first picture shows the:
Supply Board
AVC Board
Left Channel Pre-amp
Right Channel Pre-amp
Tone Control Board

The second picture shows the:
Can Capacitor (far left, can only see a bit of it)
Capacitor Board
Left Channel Driver P.C. Board
Right Channel Driver P.C. Board

Obviously there are a fairly large number of capacitors to replace, and some of them are unique, unusual, and not available today. I have a few questions I am hoping you can help me with:

- Is there a best place to start or a particular order I should go in? Should I replace the supply Board and the Capacitor Board first? Should I just go all in and replace all of the electrolytics right away?
- what the heck do I do with the can capacitor? This one seems like a particular challenge
- There are many of the axial metal sleeve capacitors, but also several wax/plastic covered radial capacitors. Should I do both types, or is one more prone to failure? I know that I can leave the ceramic ones alone.
- Most of the Axial metal sleeve capacitors are quite large in value (e.g. 1500mf, 70V) and finding like for like replacements seems to be difficult. I can get close to the right values (mF and V) but no one seems to sell axial anymore. Any recommendations or advice on replacing these? Do people have a preferred type (radial, screw terminal, other?) that works best when replacing these? Seems like Mouser has the largest selection, but these capacitors are expensive so I want to make sure I get the right one first time.

Really appreciate any tips or advice! Thanks in advance. Sorry for the large volume of questions...


Ron Rich
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Joined: Sun May 06, 2007 11:31 pm
Location: Millbrae (San Francisco area)CA, USA

Re: Rockola 474 re-cap amplifier question

by Ron Rich » Mon Jul 11, 2016 6:26 pm

IMHO, a "cap kit" is probably the best way to go here--check the above "stickies" for legitimate suppliers.
All lytics and any "wax" types, definitely should be replaced-- along with any out of spec. resistor(s). "Can type" will most likely not be offered, but under the chassis type will be sub'ed---
Ron Rich


Topic author
Torontotom
Junior Member
Posts: 6
Joined: Sat Jul 02, 2016 10:55 pm
Location: Canada

Re: Rockola 474 re-cap amplifier question

by Torontotom » Mon Jul 11, 2016 11:15 pm

Hi Ron, thanks for the direction. I tried contacting the folks in your stickies for caps.

I got a bad email return from one, and two others don't have kits for the 474. Actually Bob wrote me back with your email suggesting you might have something :D


Ron Rich
Forum Moderator
Posts: 8193
Joined: Sun May 06, 2007 11:31 pm
Location: Millbrae (San Francisco area)CA, USA

Re: Rockola 474 re-cap amplifier question

by Ron Rich » Mon Jul 11, 2016 11:24 pm

Try calling the one who's email bounced--I think he will answer--I do not have them in stock--only most Seeburg models-- Ron Rich

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