Kr9600 question

[Vintagecasey]

Looking to purchase a Kenwood KR 9600 locally. Says it used to work but got scratchy now there's no sound. Is there any quick way to rule out the
TA 200W modules? Thanks

 

[kwayde]

Have to measure voltage at the STK pins and power supply.

 

[Vintagecasey]

Long story short I purchased a Kenwood KR 9600 brand new in 1978 along with a pair of the large Advent speakers. I owned it until 8 years ago when we moved to Florida and we sold pretty much everything to make the move easier. I miss it so I've been looking for a replacement. I have a little knowledge when it comes to stereo repair, but I might be over my head but I couldn't pass this up. Okay so purchase a KR 9600 knowing that it was not in working condition. I understand the Darlington power packs are an issue but there is a guy out on eBay that has good reviews for making replacements with discreet components (I hope it's not the power packs!). I have some odd issues going on with it first when I power it on, I get no click from the relay, but when I turn it off, about a second later it clicks stays engaged for about a second and then disengages again. Never seen that happen. I took a bunch of readings I will attach them, If anyone can help me figure out if it is the power packs or if it's something before the power packs, I would appreciate any help I can get!

 

[Vintagecasey]

 

[Vintagecasey]

 

[Vintagecasey]

 

[Vintagecasey]

I was reading that the power packs pins number 1 through 10 one and three and eight and 10 are the transistor pins and to check those. Checking number one number 3 number 8 and number 10 on each pack these are the values I get that make me think they might not be burnt out? At least not the transistors?

 

[Vintagecasey]

Doing some more checks this is what I find, seems that my power supply numbers look good but my preamp numbers are all over the place.

 

[Vintagecasey]

It's Monday and back at it, pre out -power in jumpers removed, still no relay click.

 

[gort69]

With the jumpers removed, what is the voltage at pin 5 of ICe1? (it is safer to measure this voltage at wire wrap pin 6 of the circuit board 1480-10)

 

[Vintagecasey]

In the case that the TA-200-W's are not shorted, I have removed one and in the process of removing the other. Then I will check to see if I get a click or if nothing else to find out if there's a way to check them when they are desoldered from the board.

 

[Vintagecasey]

With both of the power packs desoldered and removed and the jumper is between the pre out and in removed I now get a relay click. Is that bad news for the power packs?

 

[gort69]

Yes, it is likely bad news for one of them. Almost certainly the one that had -25VDC on pin 5. The other one is probably fine since it only had 160mv at pin 5.

Hopefully, you kept track of which was which. Solder the TA-200 that had 160mv to the board that had the suspected bad one and the relay will probably click, and then you will have your answer.

 

[Vintagecasey]

Yes I marked them number one and number two number one has been five at -25.21 volts. I took some more readings with the two packs out and this is an idea of what I see.

 

[Vintagecasey]

Sorry that second reading from the top should be a number one and number 10 not a number one and number two. Don't find much information on what's inside these packs to understand which leads are doing what.

 

[gort69]

Are you doing your power up tests with a dim bulb tester?

 

[Vintagecasey]

Yes, starts bright goes pretty dim.

 

[Vintagecasey]

No, I know they're not repairable.

 

[Vintagecasey]

I soldered it back into the original spot it was in figuring maybe something on the other channel cause that one to burn didn't want to burn this one out. After putting the jumpers back in I have sound in the right channel! I bought a replacement pack from pyramid audio, I would have bought two but he only had one available. Suppose it's okay to run one of each? If you know this receiver at all, I would really appreciate bouncing some ideas off of you so I don't burn up the new one. I am a beginner when it comes to the stereo repair, I have recapped a bunch of receivers of changed out a couple bad transistors but this one here is a pretty big job. Thanks for your help so far!

 

[gort69]

It will be fine with one replacement module & one original module.

Ask away, but don’t get too in
the weeds technical. I rebuilt two or three of them about 10 years ago and repaired a couple of others, but haven’t looked at one since. Too heavy for this old man to lug around.