Looks like the direct replacement from Kenwood is the KHR-MC8601H1. Beyond that I can't find anything. Anyone out there with more skillz/knowledge than this plodder want to take a whack at this? If it's a big, copper paperweight, I can deal with it.
Added: Is there a way to test the output without serious brain fry potential?
Added: Is there a way to test the output without serious brain fry potential?
Last edited:
Dealing with mains power is always a certain risc, it's certainly not fool proof.
Technically, you need only to connect primaries and measure secondaries with a multimeter in VAC-mode. Remember, that VAC-value is usually shown as RMS, not peak (multiply with 1.42 for Vpeak).
Use a light bulb wired in series or at least a weak fuse as power limiter.
If you have no clue which wires the primaries are, it's usually the pair with highest resistance, also usually made of rather thin copper-wires.
Also, I'm not so sure wether that thing is worth the effort (in case you feel uneasy) as many consumer amps save very much on the transformer. As the amp is only 2x60W into 4R, the transformer is probably even rated below that (as it usually has only to deliver this as peak power, not continous).
Last, if the transformer is not a toroid, I maybe would not bother at all as that regularly brings more problems than it solves (humm).
Have fun and take care! Hannes
Time to glove up and don my rubber shoes and Dr. Horrible goggles.....
Is this a good place to start?
Black = primary
Black/ tracer = primary return (tracers are usually white, red or yellow)
Brown = secondary 6.3 V heater
Brown/yellow = SHCT
Red = B+
Red/yellow = B+ center tap
Yellow = 5 V filament (for rectifiers)
Green = primary 6.3 V heater
Green/yellow = PHCT
Blue = bias winding (independent of B+ winding)
Slate = bias tap on B+ winding
Is this a good place to start?
Black = primary
Black/ tracer = primary return (tracers are usually white, red or yellow)
Brown = secondary 6.3 V heater
Brown/yellow = SHCT
Red = B+
Red/yellow = B+ center tap
Yellow = 5 V filament (for rectifiers)
Green = primary 6.3 V heater
Green/yellow = PHCT
Blue = bias winding (independent of B+ winding)
Slate = bias tap on B+ winding
Last edited:
Hello Lewis, I don't know if the color coding you posted will help. That one appears to be something from the days of vacuum tubes, I doubt it's applicable to the transistorized stuff from the Japanese. I did a quick look up of your amp, Kenwood claimed 80w a channel into 8 ohms, on a 2 channel amp. Then they list the power consumption as 190watts total. Assuming this Kenwood was class A/B then it was probably about 50% efficient at best. Thus (80w x 2) x 2 again (this for the 50% eff.) you would need around 300-350w in to get 80w out on both channels continuous. That isn't happening with the consumption listed.
Now on to the next part, assuming 80w in 8 ohms, we are going to need about 25 volts DC to get 80w into one speaker. This is peak on the transformer. So the AC out is probably going to be around 18-20 volts. If they were giving you an honest 80w into both channels, the output current would be around 3-3.5 amps x 2 channels, so around 6 to 7 amps total. We know that isn't likely with the total draw.
Figuring out which wire is which is difficult without a picture of the transformer showing the colors coming out of it. Even then it might be a pain in the ****. If you do figure out the pinout of the transformer, and the voltages are around what I listed above for the AC, it might actually work for a gainclone, depending on what device you would use for the amp, and what sort of load you are planning on driving with it.
Peace,
Dave
Now on to the next part, assuming 80w in 8 ohms, we are going to need about 25 volts DC to get 80w into one speaker. This is peak on the transformer. So the AC out is probably going to be around 18-20 volts. If they were giving you an honest 80w into both channels, the output current would be around 3-3.5 amps x 2 channels, so around 6 to 7 amps total. We know that isn't likely with the total draw.
Figuring out which wire is which is difficult without a picture of the transformer showing the colors coming out of it. Even then it might be a pain in the ****. If you do figure out the pinout of the transformer, and the voltages are around what I listed above for the AC, it might actually work for a gainclone, depending on what device you would use for the amp, and what sort of load you are planning on driving with it.
Peace,
Dave
Here are some pics:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The red and white look like the primary but check. It should be the highest resistance winding. Then connect a 100w light bulb in series with it when testing. The bulb should remain off if everything is right. Then measure voltages to determine turn ratios.
EDIT: the transformer has a copper band like some switching power supply transformers. Could there be a circuit with a pair of SCRs as a primitive switching power supply? Post pictures of the original circuit board.
EDIT: the transformer has a copper band like some switching power supply transformers. Could there be a circuit with a pair of SCRs as a primitive switching power supply? Post pictures of the original circuit board.
Last edited:
Hello Lewis, I don't have the full EE, just an A.S. in EET. Started working on the Bachelor's but dropped it a couple years ago, long story. Back on topic,
Star882 suggestion is pretty much the same as what I would suggest, so you might as well start there.
Star882, those copper bands around the transformer seem to be fairly common in the Japanese branded amps, I have seen multiple ones that way. All of them were conventional class A/B amps, no switching I know of. Just thought I would let you know my observations, as limited as they are.
Peace,
Dave
Star882 suggestion is pretty much the same as what I would suggest, so you might as well start there.
Star882, those copper bands around the transformer seem to be fairly common in the Japanese branded amps, I have seen multiple ones that way. All of them were conventional class A/B amps, no switching I know of. Just thought I would let you know my observations, as limited as they are.
Peace,
Dave
Last edited:
The band is just a screening band.
I agree, red and white is most likely primary. Before you power it on, do some experimenting on the secondaries with a simple continuity test - find out which wires are part of one winding and note down the groups. Then, power on and test, as suggested use a light bulb in series with the hot wire to limit any fault current.
Treat the secondaries as LIVE until you are sure what they all do. None of them should have any continuity with the primary wires - if they do then they could be dangerous. It would be best to screw all of the secondary wires into some terminal strip that you can place probes onto, rather than holding them.
I agree, red and white is most likely primary. Before you power it on, do some experimenting on the secondaries with a simple continuity test - find out which wires are part of one winding and note down the groups. Then, power on and test, as suggested use a light bulb in series with the hot wire to limit any fault current.
Treat the secondaries as LIVE until you are sure what they all do. None of them should have any continuity with the primary wires - if they do then they could be dangerous. It would be best to screw all of the secondary wires into some terminal strip that you can place probes onto, rather than holding them.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.