DrumminDaddy
Hit it, Baby !!
With the successful repair of our KA-7150, I've piqued my daughters interest in this vintage gear that Daddy has in his collection. She jumped at the chance to look at another Kenwood classic I've got that's in need of some TLC. The venerable KA-9100.
This particular model is quite inaccesable in its physical build and layout. I figure if this thing doesn't discourage her, she's got the bug, but good. Heck, I've been putting this one off myself.
The unit has been working, but with very noisy controls. The protection relay was engaging, but sometimes sluggishly. There is also some damage to the input jack board. It is functional, but I found a replacement from a parted out unit.
At the time we opened up this amp to take a look, the protection relay wasn't energizing at all. We checked for B+ and B- voltage on pins 5,11 and 6,12 of the amp boards. That looked good. We then moved to the output of the amp boards to check for D.C. The readings on outputs, pins 7 & 8, were in the millivolt range.
While we were discussing the implications of the readings we just took, didn't the protection relay just up and kick in. The amp had been on for several minutes by then. I decided that the protection circuit would be the first thing to be addressed.
I wasn't looking forward to digging the diode board out of this amp, but I gave it a go. Sissy looked on for the better part of a hour while I painstakingly unsoldered the main filter cap lugs in order to gain access to the board. What a can-o-worms.
Whilst in the process of unsoldering the main caps, we were discussing the prospect of replacing them. I mentioned that modern caps tend to be smaller in physical size for a given capacitance, and if we replace them we may have to get creative with the leads and the clamping. She said, "Well that sucks if they're smaller, because those big caps look bad-ass."
Hehehe, 'aats me goyl !
This particular model is quite inaccesable in its physical build and layout. I figure if this thing doesn't discourage her, she's got the bug, but good. Heck, I've been putting this one off myself.
The unit has been working, but with very noisy controls. The protection relay was engaging, but sometimes sluggishly. There is also some damage to the input jack board. It is functional, but I found a replacement from a parted out unit.
At the time we opened up this amp to take a look, the protection relay wasn't energizing at all. We checked for B+ and B- voltage on pins 5,11 and 6,12 of the amp boards. That looked good. We then moved to the output of the amp boards to check for D.C. The readings on outputs, pins 7 & 8, were in the millivolt range.
While we were discussing the implications of the readings we just took, didn't the protection relay just up and kick in. The amp had been on for several minutes by then. I decided that the protection circuit would be the first thing to be addressed.
I wasn't looking forward to digging the diode board out of this amp, but I gave it a go. Sissy looked on for the better part of a hour while I painstakingly unsoldered the main filter cap lugs in order to gain access to the board. What a can-o-worms.
Whilst in the process of unsoldering the main caps, we were discussing the prospect of replacing them. I mentioned that modern caps tend to be smaller in physical size for a given capacitance, and if we replace them we may have to get creative with the leads and the clamping. She said, "Well that sucks if they're smaller, because those big caps look bad-ass."
Hehehe, 'aats me goyl !
