Kenwood model 11 recap

[Oscar23]

I found this smelly Kenwood model 11. No cord, timer broken, lights dead FM output very low, volume pot siezed beyond repair, missing knobs and quite frankly very smelly ( this must have smoked two packs a day). Put a cord on it bypassed the timer and we had power and sound (very muddy sound)

 

[Oscar23]

I started with the power supply. Very cooked. Replaced caps, qk1(2sc1419 with bd239),rk4,rk6, and dk3. Looks much better now. All voltages are now up to spec on to the amp. Tons of glue on this thing to.

 

[Oscar23]

I did the amp board today changed all caps and putting new trim pots in. Passed the dbt. Scrapped all glue off the board.

 

[Oscar23]

Forward progress is always a motivator. Keep goin'! ...and if you have time, take a step back and have closer look (read: measure) at R1, 2, 3 & 5 on the PS board. Carbon composition resistors have a tendency to get quite a bit out of spec over time and heat. Otherwise, carry on.

I took your advice and measured them they were out of spec like you said replaced all of them

 

[Oscar23]

The pre amp board was and adventure to get to has to remove the whole front part of the chassie. Quite the mess speaker selector board and switch board left hanging. Removed the volume pot.

 

[Oscar23]

Tried again to get the volume pot to turn on its own no such luck. It was seized sold. Repaired the seized timer. Opened it up and added 3 in 1 oil and moved it slowly now turns freely. No to just fix the shaft.

 

[Oscar23]

Those red "tear drop" shaped caps on the preamp board are tantalum...film cap replacements might make a worthy upgrade. Lookin good![/QUOTE
What would make a good replament? Can I still get tantalum caps

 

[Oscar23]

Dijjikey does not have any 3.3 uf 10v I can 3.3uf 450 VDC

 

[Oscar23]

Use the next voltage size higher than 10V that's available...16V, 25V, 35V, 50V?

50 v is the next up

 

[Oscar23]

I have to wait for my volume pot to arrive I ordered a replacement so I took the time to clean the faceplace and all the boards while I had access to them.scrubbed all that nicotine off

 

[Oscar23]

I replaced all the tantalums. Put my volume pot in cleaned it all up and put the model 11 back together. Everything works and sounds great. Except there is no lights and there is a pop when I turn it on.

 

[Oscar23]

Its the model 1 there is no lights at all. I had 0 MV at the terminal

 

[Oscar23]

All the fuses are good. I think it is in the power supply. Going to pull the diodes and test them again. As for the pop not sure yet about that one I thought DC first to but none to set I going to recheck the amp and see if there is a loose cap or something.

 

[Oscar23]

Perfect thanks

 

[Oscar23]

Out of curiosity how do you know by looking at the schematic that q1-4 are differential pairs regulating the offset I often wondered how to figure it out

 

[Oscar23]

I watched the video kind of get it

 

[Oscar23]

Ok if you look at the service manual the idle current is 45ma for one side and 45mv for the other obviously a mistake witch do I use I know I put at 45mv it goes right into protection

 

[Oscar23]

So if I have to lower the idle current down to keep it out of protection I should check the transistors.(q19,20,21,22,23,24,25,26)

 

[Oscar23]

Its at 35-40 MV right now pretty steady. So not extremely low could that also be what's causing the popping

 

[Oscar23]

Yes it was switched to A the pop is only when I power on I will clean the switch in the morning and double check the DC again