Yamaha CR 620

[Fridge]

Recapping and cleaning up an old Cr 620. All good, just noticed that 2 transistors on Main Circuit Board are Getting very hot. Signs of slight board burn around the heat sink. TR802, 803. CHecked Diodes and are good. Idle current is good as well. Is it normal for these transistors to get very hot? If not what ideas on what may be the trouble spots? By the way with new caps and cleaning this unit sounds very good. Thanks

 

[avionic]

Is it normal for these transistors to get very hot?

Yes. Thats why they have heatsinks.

 

[Fridge]

Thank you. .

 

[Fridge]

Hey avionic, I also am cleaning up a CR 440. It sounds great too, but I can't seem to get any reception on the tuner. It is very week and sounds like some sort of short going on in this section...any suggestions to help with this issue? BTW, I can sut my stove off and cook eggs and onions on that heat sink

 

[avionic]

I can sut my stove off and cook eggs and onions on that heat sink

If you have a service manual check your bias/idle current adjustment.

 

[avionic]

I can't seem to get any reception on the tuner. It is very week and sounds like some sort of short going on in this section...any suggestions to help with this issue?

Are you using any sort of antenna ?

 

[Fridge]

I used a Dipole antenna, made no difference at all. The signal meter barely moves. Idle current is set to spec on service manual. All other inputs work and sound good?

 

[avionic]

Idle current is set to spec on service manual.

What impedance are your speakers ?

 

[avionic]

I used a Dipole antenna, made no difference at all. The signal meter barely moves

Hows your superheterodyne alignment skills ?

 

[Fridge]

I have it hooked up to a pair of Minimus as my bench speakers..about the alignment, there is a first time for everythin. I am not afraid to give it a shot!

 

[avionic]

I'm betting you don't have the test gear to do the alignment properly. ie FM signal generator , oscilloscope , frequency counter or distortion analyzer.

 

[Fridge]

I would not take that bet! Ha. I thought about getting that stuff, then after a short thought, I thought not, due to I would not have a clue what to do with it. That gear is expensive even used stuff on auctions gets pricey. I don't think the unit is worth sending off.

 

[Fridge]

Well, I dropped my screwdriver on the front end board and bam! I have perfect reception! Sadly it is after I poked around the trim pots and now I have a hum in the tuner section as I increase volume and I knocked the dial gear loose and broke the string! 1 step forward 3 back...its ok I will just keep playing..avionic

 

[avionic]

The service manual usually has a dial string diagram.

 

[avionic]

Page 9

http://akdatabase.com/AKview/albums/userpics/10007/Yamaha CR-620 Service Manual.pdf

 

[Fridge]

thanks for the link,,,,more fun to have!

 

[Fridge]

must have been a solder bridge or something similar that I loosened when I dropped the screwdriver. I was about to get PO'd and tear the unit up for parts.

 

[avionic]

thanks for the link,,,,more fun to have!

Fun..Right.. Not my favorite thing to do.