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Yamaha CR-2040 Clean Up

rickknight said:
Hey everyone, I've been away from this project for almost 2 years, but I'm back at it now and want to get it finished. However, I've run into a snag. All of the interconnects in this receiver are wire wrap connections, so I decided to get a wire wrap tool so that I can unwrap, and then rewrap the connections to each board. The unwrap part works great, but it turns out the wire Yamaha uses inside this unit is like a soldered speaker wire, and it doesn't rewrap well at all. Now I'm looking for an alternative. I don't really want to use solder so I'm looking for some sort of header pin connector. I thought the connectors like the ones used in computers might work, but they're too small. does anyone have a suggestion for what to use to reconnect these wires. By the way, the pins measure 1.00 mm, see the photo below.

Thanks,
Rick
Click to expand...
Bad idea...You can not rewrap once unwrapped....How many wire wraps have you screwed up ? Just that one ?

If you need think you need to get wire wraps off the board. Unsolder the wire wrap header from the circuit board and leave the wire wraps unmolested.
 
It's tinned wire and once wrapped and then unwrapped it's lost it's rigidity, you can try re-tinning the wire with solder and wrapping again. Even normal wire wrap wire will not rewrap it will break. Wire wrapping does make a very good connection as the corners of the wire wrap post dig into the wire but those nicks in the wire will cause it break when unwrapping or just moving the wire around too much. Great for manufacturing but not so great for maintenance.

Craig
 
Avionic, thanks for the quick reply. Yes, re-wrapping is not a good practice. My plan was to strip back the wire a bit and then rewrap the fresh end, however most of the wires don't have enough play in them to stretch far enough for that. I'm trying to avoid soldering. By the way, I did not try to rewrap the one unwrapped wire, I just straightened it out for the picture, all other connections are Yamaha's work. Any other suggestions?

Thanks,
R
 
Craig, If I can tin the header pins I can solder the wires, I was just hoping for another option, some sort of plug that could be crimped to the wire and then slipped over the pin.

Thanks,
Rick
 
rickknight said:
Craig, If I can tin the header pins I can solder the wires, I was just hoping for another option, some sort of plug that could be crimped to the wire and then slipped over the pin.

Thanks,
Rick
Click to expand...
Just clean that pin with scotch bright and wipe down with alcohol. Tin the pin and solder that one wire.
 
Soldering the unwrapped wire worked out OK. All the caps and fusible resistor replaced. Now I'm cleaning things up before I put the board back on the heatsink. I want to get rid of all the old grease so I've cleaned off the backs of the transistors and the heatsink, now I want to clean the mica insulators but I'm having a heck of a time getting all the grease off without bending them. Can you recommend a source for new insulators, or a simple way to clean the old insulators? They go under 2SD736A and 2SB700A transistors.

Thanks,
Rick
 
I usually lay the insulators on the bench top and use a dry paper towel to wipe one side off. Then flip them over to wipe the other side off.
You can get new insulators from B+D Enterprise
MT-200 is as close as your going to get..I'd try to salvage the originals.
https://www.bdent.com/mica-mt-200-10-pack.html
 
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Thanks Avionic. I've tried wiping the grease off, but some of it refuses to let go. I've checked Digikey, Mouser, Part Express and others and couldn't find anything close to fitting. Thanks for the link to B+D. I had never heard of them before. I purchased a 10 pack, so I'll have a couple of spares.

Thanks,
Rick
 
That looks like an excellent resource, but I don't see a cross reference. Do you have a goto cross reference?

Thanks,
Rick
 
rickknight said:
That looks like an excellent resource, but I don't see a cross reference. Do you have a goto cross reference?

Thanks,
Rick
Click to expand...
No they have no cross reference..
I use datasheetarchive for cross reference.
 
Finally done with the first round of re-capping this receiver. I have not done the DC offset adjustment yet, that will be tomorrow. So far, I think I hear an improvement so I'm happy. After the offset adjustment I'll try to work on other parts of the audio path, not too interested in the FM section and I don't have the alignment equipment or experience. It looks like I can remove the bottom panel to access the solder side of the Equalizer, Tone, MC and Phono boards/areas. Before I pull the bottom, can anyone confirm that for me?

Thanks,
Rick
 
Just about ready to tackle the phono board but I have another question. There are 4 (2 per channel) silver/transparent components on the board that I'm not sure what they are. You can see them in the attached image. Can anyone tell me what they are, and what would be good replacements, assuming they are capacitors? You can see them just below and to the left of a bank of 3 resistors. I'll need to pull the phono board in order to recap it. When I do, I'll send more pics.

Thanks,
Rick
 

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rickknight said:
what would be good replacements,
Click to expand...
Polystyrene is the best..There is likely absolutely nothing wrong with the originals.

They do not tolerate very much heat ie. unsoldering/soldering can easily damage them.Must use a heatsink clip when soldering.
 
Thanks Avionic, I'll leave those 4 alone then. The phono board is small and only has 10 electrolytic caps on it, but the board soldered upright onto the main board near the back of the unit so I need to remove it to work on it.

Thanks,
RIck
 
Looking for more advice. I've pulled the phono stage board and am ready to order parts. The original parts are Nichicon, Nichicon SE, Nippon Chem Co SE, SL and a couple labeled M and CE (no brand). Since there are only six caps per channel, cost is not really an issue and since my primary use will be listening to vinyl, I want the phone stage to be as good as I can get. Any recommendations?

Phono_board_b.jpg Phono_board_a.jpg
 
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