CR-620 Not Functioning

kosmaras

New Member
I purchased a CR-620 on eBay that the seller said EVERYTHING worked on. I received it today, and oh surprise, nothing works.

I borrowed my dads CR-440 to make sure my TT and speakers worked and sure enough, they do and sound great.

The CR-440 has a "click" after you power it on, and the 620 does not. I filed a complaint with eBay to get a refund, but if I get stuck with this thing I'd like to look into finding out what's wrong.

Does anyone have any tips on what to look at as a root cause?
 
CR-620 quiet

Hello kosmaras

Bad news !

The click after the power on is the activation of the relay when everything is fine .
If the relay do not works it is because one channel is out and DC offset is inside the unit .
One output is out because one (or more) output transistor is shorted and power supply voltage is present at the output of the amplifier !
To avoid total destruction of your speakers the relay is not actived !
I think the best way is to claim the repair amount to the seller no other way if you like this unit

Come back to us if you need any other info
 
The above would certainly be the most obvious/common problem, but there could be simpler problems with the relay circuit too. Where are you?
 
I love my CR-420. Hope you can get yours working, or returned for credit. The 70s CR series is wonderful.
 
Keep us updated. If you keep it, there are a lot of people here who can help you get it working.
 
Thank you again for all of your advice. The seller has given me a full refund and didn't include any funds to ship him the receiver back. So it looks like it's a restoration project!

Does anyone have any idea on where to start to find the short on this thing? I'm FAR from an electrical guru, so this will be quite the learning experience.

If it means anything, the power and FM light come on, but not any of the other lamps. Hopefully someone has an idea on what transistor to look at first.

Thanks!
 
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Thank you again for all of your advice. The seller has given me a full refund and didn't include any funds to ship him the receiver back. So it looks like it's a restoration project!

Does anyone have any idea on where to start to find the short on this thing? I'm FAR from an electrical guru, so this will be quite the learning experience.

If it means anything, the power and FM light come on, but not any of the other lamps. Hopefully someone has an idea on what transistor to look at first.

Thanks!

Well first we need to determine if there is any DC voltage present at the outputs of the two amplifiers. This must be measured at a point before the protect relay contacts.
 
Hi! I read jpowell1's thread where you assisted him in fixing his 620, but a few things are still unclear to me.

I'm reading the schematics, but I don't know a good place to measure the DC voltage before the relay.
 
Look on the main board. There are two large copper coils of enameled wire ( L701 and L702 ) Scratch a bit of the enamel off of them , enough to make a good electrical connection for your multimeter test probe. Connect your black test probe to chassis ground. Measure the voltage on the coils 701 and 702. Hopefully its just a few millivolts.This measurement is your actual DC offset/balance before the relay.
 
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