**SOLVED** On the protection board I installed Q2 (2SA1220) backwards. Re-installed in the correct orientation and now it works perfectly.
Watch those pin-outs everyone! I feel so silly and so relieved at the same time.
Both pins 9 and 30 on the main amp board have ~3.87 volts.
Again, I assume this voltage should be 0 volts. I've tried tracing this voltage throughout the main amp board and all components test fine. No bad resistors, I've replaced all electrolytic caps, and tested all transistors for shorts...
A-09 on the Protection Board? I have readings of the following:
Pin 1 = 0.110 v
Pin 2 = 0.052 v
Pin 3 = -0.012v
Pin 4 = 0.055 v
Not exactly 0 volts, is there adjustment for this or does it indicate something elsewhere?
Hello everyone! I looking for some help with a Kenwood KR-8340 Two Four Receiver. I've read through every post I could find about this family of receivers (KR-7340, 8340 & 9340) but haven't been able to narrow down my problem.
When I power up the unit with a current limited variac, I get no...
I removed the incorrect 4.7k ohm resistors R626 & R627 and installed the correct 4.7 ohm resistors. It's working!
Class B Mode bias was set at 50 mV
Class A Mode bias at 850 mV
It sounds amazing, really. I've had a chance to listen to a lot of cool vintage sets and amps but this CA-800 is...
Just checked some photos of the rebuilt amp boards...
R626 & R627 are supposed to be 4.7 ohm according to my schematic. Can I get a sanity check on that?
From my photos I can clearly see that I installed 4.7k ohm resistors in both location on both boards :no:
Time to go back and check all...
Yeah...because both boards are affected/behaving the same way I'm really lost.
I'll go back and check D603,4 and start a list of the voltages for the transistors. (may take me a few days to gather and post).
As for the fuses, F602 on the Left Amp Board was blown when I first got the unit. I...
I also wanted to note that on the Right Amp board, when the unit is powered up in Class B mode, There is definite ringing (oscillation?) noise coming from the bi-polar 47uF capacitor that sits between TR604 and TR601.
If I touch it with an insulated screw driver, the bias drops 1-5 mv and the...
I did note the pin-out difference and installed them accordingly. And TR605 was replaced with a KSC1815. It was turned 180 degrees from original transistor orientation, so the pin-out should be correct. It may be difficult to see in my photo (because of the heat shrink I used) but TR604 and...
Here's the readings I got this weekend. I'll have to go back tonight and follow mbz's list of readings as they are more comprehensive:
Mode------Pins------L-------R--------
Normal---BC----0.9ohms--0.9ohms
SC----480ohms--484ohms
AC----8.06K ohms---8.1K ohms
Class A...
For testing the Ohms verifying the switch is functional, in NORMAL mode I should have something like this:
Normal:
B-C <1 ohm
S-C ~470 ohm
A-C >5k ohm
Class A:
A-C <1 ohm
S-C <1 ohm
B-C >5 kohm
Or do I have that reversed?
Thanks avionic, I have 5k Bourns Multi-Turn trimmers installed. I'll double check the wiring from the amp board to the mode switch. Just to be clear, these are the wires you're talking about right?:
Amp Board SCBA Wire by ekimezeerf posted Jun 9, 2018 at 1:29 PMOp Switch CSBA Wire by ekimezeerf...
Hey everyone, long time lurker, first time posting.
A friend brought me a dead CA-800, would not power on and many signs of heat stress on main amp and power boards. Our thought was the PO has dumped a bottle of cologne on it due to it's aroma and the goop present everywhere inside.
I've...