Kenwood L-07mII overheating! Help needed!

I did the usual recapping job for a pair of L-07mIIs, plus the replacement of all pf caps in the driver board, as per Echowars recommendation in AK's thread about the L-07mII's oscillation issues.

I was restoring a pair, the first one came out just fine, but I messed up the 2nd one, while I was measuring the bias between points 10 and 19. First, I could not get any reading (the amp was working fine prior to restoring) for the bias. While measuring, I accidentally shorted a couple of the pins of the interface between driver and main board, which caused both 5A fuses to blow. I replaced the fuses, but now resistors R14 and R15 get very hot and resistor R19 gets RED hot! Newly installed C8 also gets very hot to the point the cap got bulged. While the amp was on, I tried to measure the bias, but even with the trimpot fully counterclockwise, the lowest reading was about 40mV.

Oddly enough, I managed to pull off another driver board from a working L-07mII and, this time, R36 got hot to the point of melting the solder. I am now wondering if I fried my driver board, the main board or both.

Any feedback from seasoned Kenwood fans is greatly appreciated. Thanks.

Pull and test all the outputs. If they look OK, then I'd be tempted to set them aside till I had things sorted out, and install one MG21193 and one MJ21194 to complete the feedback loop for troubleshooting.

Anyway, with the resistors you're talking about burning up, I'd be looking at Qe14 & Qe15, and Qe7, 8, and 9 as well.

EchoWars said:

Pull and test all the outputs. If they look OK, then I'd be tempted to set them aside till I had things sorted out, and install one MG21193 and one MJ21194 to complete the feedback loop for troubleshooting.

Anyway, with the resistors you're talking about burning up, I'd be looking at Qe14 & Qe15, and Qe7, 8, and 9 as well.

Click to expand...

After a LONG hiatus, decided to tackle this. Qe14 and 15 are 2SC1913 and 2SA913. Qe 7 & 8 are 2SA899 and Qe9 is 2SC1904. What would be modern replacements?

2SC1913 -> 2SC4883
2SA913 -> 2SA1859
2SA899 -> 2SA1209
2SC1904 -> 2SC2911

Digikey for the C4883 and A1859, and B&D for the A1209 and C2911.

Thanks Glenn. Are these same pin configuration?

TO-220's all have the same config, but the TO-126's may or may not. Download the data sheets to make sure.