• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

CR-620, do clean board drawings exist?

3

33713

Active Member
Hey all, I am working on a 620 recap. The boards are so poorly marked. Also, the service manual scans are impossible to read, at least for me. Are there any clean versions out there? Olegs rebuild thread has been helpful, but I am tring to replace the preamp parts that are on the tuner board and finding it tough to figure out. Any thoughts? Thanks

These:

This board also houses four low-leakage capacitors (C671, C672, C677, C678) from the tone control circuit. All of them were replaced with modern Nichicon UKL low-leakage capacitors.

Test results on the original capacitors removed from the rest of the tone control circuit:

C671 rated capacitance – 10uF, measured – 10uF, ESR – 2.3Ω, deviation: 0%
C672 rated capacitance – 10uF, measured – 11uF, ESR – 1.9Ω, deviation: +10%
C677 rated capacitance – 2.2uF, measured – 2.1uF, ESR – 3.8Ω, deviation: -5%
C678 rated capacitance – 2.2uF, measured – 2.2uF, ESR – 3.7Ω, deviation: 0%
 
Register to hide this ad
I have a reasonably clean schematic but everything else with board layouts and stuff is pretty lousy. The couple 620s I've worked on had a lot of bad caps. There's a write-up on my site with some values.
 
ConradH said:
I have a reasonably clean schematic but everything else with board layouts and stuff is pretty lousy. The couple 620s I've worked on had a lot of bad caps. There's a write-up on my site with some values.
Click to expand...
Thank You. I did take a look at your page recently and see your note about mirror imaging the traces to plot the locations.

I may or may not be able to figure that out, somewhat of a remove and replace still, but used to marantz boards and manuals haha
 
Nashou66 said:
try analog alley , they have super nice service manuals
Click to expand...
Ok, ty, I am done with the amp, power supply, and tone board. I really just wanna nail down this continuation of the tone circuit and be done with, meaning I would prefer not to send money to buy it. I am gonna skip FM due to the alignment aspect.
 
What do you need to know about the tone signals? Without the right equipment you can't do a full FM alignment, but you can probably touch up some of it with regular FM radio broadcast signals.

The mirror imaging is easy. Take pictures with your camera, cell or whatever, then use the free Affinity photo editor to flip them. I also use that to clean up crummy schematic and board scans, but there's a limit to what you can do.
 
Ok, so according to Olegs restoration, there are 4 caps that belong to the preamp/tone circuit. I want to change them so I am done with my project unless I dig deeper into it later, meaning FM and phono. Ty
 
Did the preamp section as described on this board, now I wonder maybe just do the phono before I put this back together. Would 1000uf UKA's cause any problems in the 470uf 515,516 locations? I am out of 470's
 
You must log in or register to reply here.
Back
Top Bottom