Techie question..heads up Echo or SolderIron

ProAc_Fan

Addicted Member
How would I go about finding out which OT(s) in my Yammie CR-840 receiver have shorted out? PLease spoon feed me as I'm new at this attempt at servicing gear. THe receiver was working perfect when I got it, then in a few months I was hearing some clicking noise through the speakers when the protection relay kicked in. Finally one day on startup the fuse blew and now the fuse blows immediately when trying to fire it up. Any thoughts or opinions would be appreciated.

TIA Mike
 
If the OT are in a socket type plug and you can remove them, go ahead and take them out one at a time. If you can get that far let me know and i can tell you what to do next, do you have an ohm meter or DMM?
 
i mean just see if they are, if so you can take them out but remeber which went where, or we can do one at a time.
 
Yeah I have a multimeter but I haven't even located the OT's yet. Mind you I haven't removed the bottom cover yet but I will tomorrow. It's getting late here in the northeast. We'll work on this tomorrow.

Mike
 
Weird. I can't find anything resembling the OT's from my PL 400amp. Underneath each heat sink there's a large 4"X4" chip with Yamaha power amplifier written in them and part number IG 02970. They appear to be held in place by 2 screws. Would those be the OT's? Should I remove them for testing? Can I kill myself in any way taking these out? LOL


Mike
 
because the reciever was made in early 80's im assuming it had the roundish type OT's i forget what these are called. but i just had to test the ones on the Phase Linear amp i got so i know how to do it at least. and ive had some experience with repairs. This PL would be my second.
transistor.gif
I imagine they will look like the big one at the top of pic. hopefully you can see if they are in a socket or soldered leads.
 
do you happen to have a digital camera? If its 4 inches x 4 inches i dont think thats them. ive never seen one that big! should be mounted right on the heat sink and a few of them. You cant kill yourself taking them out. but i dont want you removing anything until i know what it is lol. of course, dont have it plugged in while your in there. If it doesnt look like that metal can one in the other pic it probbly looks like the one in the top right in this pic. If not im kina stumped!.
transistor.gif
 
Those IC's look like about a 16pin chip. I think those must be the OT's. They aren't like the discrete type found in the Phase Linears.


Mike
 
I really have to get to bed. I'll post pic tomorrow. These chips( one under each heatsink) are the only things anywhere near the heatsinks.

Mike
 
Yes. go to bed! It doesnt sound like anything im experienced with so i probbly cant help you!. Too bad. I thought i might actually be able to help someone! lol
 
After we get MartL to put away the hand lotion, I'll answer...

Done?

Good...

Looks like the Yammie uses a output pack of sorts. Kenwood pioneered this sort of thing. It's probably not an IC in the conventional sense, but a collection of devices sharing a common heat sink plate. A lot of advantages to doing this, and the only drawback is parts availability.

If you have a manual, post the schematic. If not, I'll say the same thing to you that I say to everyone: If you have a piece of equipment that you do not ever intend to part with, get the damn schematic/service manual!! Always good to have, you may learn something, and hell, who knows, next week they all may disappear.
 
A 4"x4" chip with 16 pins and mounted on a heat sink.... It must be one whole amplifier channel. If the package is smaller say 1.5"x 2" then it would be the normal 2 or 4 output transistors and their bias circuit in one package. What you have there is a hybrid circuit. A fancy name for taking the transistors, resistors, and diode without their cloth/ case, so what you have is the bare chips, and mount them on an insulating but heat conducting board before put on a plastic cover. It is a pain in the ??? to get a replacemant. I ran across a few with STK type numbers and they are easy to get at $20 each or per channel. You may have to do a bit of research to get a drop in replacemnet.
 
It seems to be s..... like this.I don t like this beast with a lot a legs :D ...
In general they are pricey
this one was a STK 439 and it s dead!!!
 
Last edited:
Let me know where you find a good source for those things. I've got an 840 (or is it an 820? need to look) that has the same problem. IIRC they cross to an NTE number but they're PRICEY. I want to say the number ends in 0031 or 0032. Something like $35 each last time I looked. BTW mine got smashed in transit and has a loose tuning knob shaft. The mount is wrecked. Anyone know where I can scavenge a replacement?

Thanks
Mike
 
The 840 used STK power paks. they are amplifier modules.

check places like parts express, mcm electronics, digikey, newark etc... and do a search for STK
 
thanks David
I found one to repair a little hitachi for 15 bucks not a steal but not to bad usually these hybrids are very expensive...
a little pic of the hitachi raised from the dead;)
 
OK, this was posted elsewhere, but here we go;

The ICs used in the CR-n40 line (and probably every other brand) were re-badged Sanyo ICs. AudioLab of Georgia sells them at decent prices. Unfortunately the ones for the 840 are out of stock at the moment. That's the bad news, the good news is that the ones used in the n40 series are electrically identical, so use the ones for the next higher receiver, the 1040. Part number is STK0080II and if in stock are $15 each + shipping.

If anyone has other n40s I can get the cross reference.

For your loose tuning knob, try this; at the end of the shaft where the dial cord is wrapped aroung there is a collar with two screws. Loosen the screws and push the collar toward the flywheel. Also, sometimes the nut behind the panel comes loose, but you will have to get a long Allen wrench to get the knob off and then deal with the &^%$ gorilla that tightened all the panel mount screws. Finally, if none of the above solves your loose flywheel problems, I have the assembly from a 620 parts unit you can have. Use Google to find AudioLab.

Rob
 
stk0080 also crosses to a SK 10007 Listed as a AF Power amp 80W I think since my R-700S Use this set up I may pick up a few.:D

Also coverts to a NTE 1322. Might pick up some of each and do a
A/B test with them
 
Last edited:
Back
Top Bottom