Receiver Troubleshooting - No Power

[Florizel]

I bought a lot of "vintage" receivers at a bankruptcy auction. They all look cool. None of them work.

So this is a learning opportunity! I am staring now at a Kenwood KR-77 receiver. Nothing special but heavy enough to anchor a small cabin cruiser! I'd like to try to get it to do something, anything.

The face will light up but that is all it will do. Tuner section won't twitch the meter. Not even static from speaker or headphone outputs.

What is a good sequence of steps to walk through to figure this out? Like I said, this is a "learning experience."

 

[tyeeslayer]

Download the service manual from hifiengine and get a multi meter.

 

[Florizel]

Download the service manual from hifiengine and get a multi meter.

I have the manual. I have a multimeter. Thanks but I was hoping for something a bit more specific in the way of "likely suspects."

 

[blhagstrom]

Any pre-out/main-in jacks in the back? Are they connected.

Plug something else into it (CD player) and see if anything comes out the speaker jacks/headphone jack/tape out jacks.

Study the service manual, checking power supply voltages is probably going to come up sooner or later.
IF there are any fuses hiding, check them with a meter if they don't look blown.
If they are blown, build a Dim Bulb Tester and get ready for some serious repair work OR bail now.

 

[petehall347]

looks to be cap coupled so i would expect a fuse for each channels b+ .
you could try measuring dc voltage at speaker terminals first without speakers .. i would expect to see a few volts on unloaded outputs if they are working .

 

[century tek]

Maybe a pic underneath? Can't see the manual. Does it have a protection relay underneath?

Likely suspects? Check voltages compared to the schematic. Check for bad output transistors. Check capacitors in power supply. Check diodes in power supply. Sorry to say but you are just going to have to do these basic troubleshooting techniques.

Thanks but I was hoping for something a bit more specific in the way of "likely suspects."

You sound like a novice if you need us to point to something more specific.

 

[petehall347]

well i just checked the manual ..not a fuse in sight ..i am surprised ..
there does appear to be pre main switch .. try a jumper cable from pre to main to bypass the switch
if no joy with voltage at outputs look at dc voltages cathode end of d2 and d3 power supply

 

[petehall347]

Maybe a pic underneath? Can't see the manual. Does it have a protection relay underneath?

Likely suspects? Check voltages compared to the schematic. Check for bad output transistors. Check capacitors in power supply. Check diodes in power supply. Sorry to say but you are just going to have to do these basic troubleshooting techniques.

no relay .its cap coupled

 

[comish4]

Check and see if the output transistors are shorted if none of them or shorted then go back to the power supply diagram and study the travel of the power supply.

 

[petehall347]

i am suspecting there will be fuse links on the pcb boards .. check for burned traces
another test you can do is measure collector voltages at the output transistors collectors ..this happens to be the cases ..outer ones should be 48v ..inner 2 24v all dc volts

 

[Eastham]

It does appear to have pre in/ out jacks on the back. OP check that those are jumpered like this:



You will get the exact situation you described if they're not jumped.

 

[Watthour]

Beware the germanium.