Kenwood KC-6060 intensity problem

pakko

Member
Hello.

I have a nice KC-6060 scope and had it stored for some years. It´s still working but I need to turn the intensity up all the way to get a picture.
After 10 minutes the scope disappeared totally. I need to wait another 10 min. switching off the unit and then it works again a few moments....!?
Today I changed the caps with no result. I do have a manual - could someone give me an advice which part/transistors may be faulty! Or in which direction should I look.
Thanks a lot
Greetz from Hamburg/Germany

Eckart
 
I'm not an expert, this is just some info or direction that can hopefully help you out. It could be a number of things such as the actual scope tube could be going bad or the "intensity resistors" may need to be replaced?
You say you have a manual. Is it a "User Manual"? If its a user manual that really won't be much help. You need a "Service Manual" or at least a schematic of the unit itself. Try and get a service manual if you can.
I was able to find a schematic for the Kenwood KC-6060 that you can download for free from www.hifi-manuals.com. just sign up. Once you download it first check on the intensity resistors and check their values or just out right replace them. These are variable resistors so make sure you replace them with the same resistance values. I believe, from looking at the schematic they are VR2 (500KB) & VR107 (250KB) located around section 3-H (use the edge of the schematic numbers and letters).
As I said, not an expert, but I'd start there then move on to the actual scope tube itself.
Good Luck and keep us posted on your findings.
Hopefully someone else with more knowledge about this will chime in with helpful info.
 
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thanks for your input!
VR 107 is the pot/knob on the front of the unit. VR 2 is a trimpot for the spot killer - both are fine. I guess more a problem with the FET Transistors Q1,2 & Q9,10 in the amp section. The output voltage at the pins 5,6 and 8,9 is to high in my scope. It´s around 140V.
Although I can´t get the 1,4V at the Transistors Q 1,2,9,10.
These are 2SK17 - hard to find a replace.
But still I´m not sure about it.
All the other voltages are so far OK.
e

PS - I do have a service manual - even in paper;)
 
here a cut off from the manual....
 

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OK - I changed ALL the 2SC458´s (to BC550C) on all boards and one of the four 2SC627´s (to 2SC154)
with the result than the scope is working now so far but I still need to turn up the intensity (more than 3 O´clock) all the way to get a good picture.
I changed one of the 2SC627´s because on this output line the voltage reading was extra high. But I have still to much Voltage on the outputs - Pin5=134V, Pin6=124V, Pin8=132V (here I changed the Transistor was before 180V!), Pin9=132V.
At the board "1008" the readings are: Pin3=130V, Pin4=26V, Pin5=-6.5V, Pin1=300V, Pin2=220V
So far the results.....
eckart
 
Multivoltage unit? Set for the appropriate voltage? If there's a setting for 230~240V, that's where I'd put it.
 
Yes, Multi-Voltage and adjusted to the right settings - 220/240V.....
Today I checked the resistor behind the intensity pot (1M) - but it´s OK.
At the moment no other ideas from my side.
Scope runs with intensity pot at 3 o´clock and after a while I need to turn it full CW. That´s the situation.
e.
 
I think I'd be attacking the old electrolytics by now. And maybe look at replacing Q2 on the UM-1008J board (the transistor that does the spot killer).

And it's certainly possible that the old tube has simply seen better days, but I'd not conclude that until I had tried everything else.
 
Thanks again Glenn - the only Elytic I didn´t changed are the high voltage oil caps.
Q2 is checked and OK - I can adjust the spot-killer without problems - like everything else - I´m with you and think the tube is getting bad slowly.
 
Know that the Japanese PIO caps (paper-in-oil) were not terribly trustworthy, unlike the USA and European caps of the time. I don't have much experience with the unit to say whether the ones in the 6060 are problematic, but who knows?

FYI, the cheap Leader LBO-310 scope is supposed to use the same tube.
 
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Q2 is the transistor that connects pin 3 of the tube (brightness control) to the pot- this particular transistor is dual function, brightness and spot killer. How did you check q2? Did you measure the collector of q2 at power on vs when the display goes away? Was it the same voltage?

I have one of these units, all stock, cool piece of gear.
 
This could be a good point.
I unsoldered the 2sc984 and checked it with the transistor tester. It looked OK.
But just in case I can replace it.
What would be a suitable replacement?
A BC337 or BD137?
e.
 
This is the same transistor used in the bias circuit of the early production 2270's, the round one for heat compensation. bc337 will work if you have one, BD is even heftier.
 
Hello again.
Today I first of all checked the voltage drift at the collector of Q2 with the 2SC984 - and yes there is a drift - voltage goes down after a while!
So I changed the transistor to a new 2SC3117 (I had nothing else to my hands)
and - the same thing - voltage goes down after a few minutes and picture fades away.
Result? Tube to old? It seems to be not the transistor Q2
e.
 
No - I don´t.
Just this minute I played around with the adjustment of Astigmatism and spot kiler. It´s possible to to get a better intensity if I do not exactly what´s described in the manual.
First I adjusted the Astigm. as described - but then I changed the Intensity at the front pot to middle position and do then the spot killer adjustment.
Now I have a better intensity at even 12 o´clock.
I think I stay with this!
 
Finally two pictures of the whole Set.
thanx everybody!

:music:
 

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Damn dude! :thmbsp:

You've got a beautiful vintage Kenwood audio setup there! :tresbon:

That looks Sweet! :yes:

Thanks for posting and sharing! :D
 
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