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H&K Tubeman II - Problems with sound
H&K Tubeman II - Problems with sound
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Old 28th March 2019, 05:45 AM   #1
vooltool is offline vooltool  Kazakhstan
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Default H&K Tubeman II - Problems with sound

Hi everyone!

I have guitar preamp H&K Tubeman II. And, recently , I got a problem: when i begin to play, the sound is good and power, distortion is great too. But after 10-15 minutes sound changes and distortion doesn't same when i have started. It is more poor, hasn't power.

The preamp is not young, around 12 years old, but i use it seldom. I had supposed, may be electric capacitors have dried, and i have changed all of them. It didn't help.

I have iron and multimeter, but I don't understand electronic. I hope, may be you offer some advices what i can change or check in preamp.

Thanks in advance!
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Old 28th March 2019, 01:02 PM   #2
hex69 is offline hex69  Canada
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Can be solder joint that has cracked. I experienced this once, they weren't trouble until the amp heated up and the joints would open up, they were small and very hard to find even with a magnifier. I would look around the tube socket

Last edited by hex69; 28th March 2019 at 01:07 PM.
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Old 29th March 2019, 01:29 AM   #3
Printer2 is offline Printer2  Canada
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First thing I would think is mechanical connection. I would spray the connector for the tube.
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Old 29th March 2019, 06:06 AM   #4
vooltool is offline vooltool  Kazakhstan
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I did two photos. If need more, i can do it .
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Old 29th March 2019, 12:06 PM   #5
Printer2 is offline Printer2  Canada
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Sorry, from the schematic I thought there might be a ribbon cable connecting the tube board to the main board. H&K has pins on the tube board that gets soldered into the main board, no connector.
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Old 29th March 2019, 12:51 PM   #6
vooltool is offline vooltool  Kazakhstan
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Again some photos
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Old 29th March 2019, 01:49 PM   #7
hex69 is offline hex69  Canada
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I'm no expert for sure, most of the people around here are way better and some of them are professionnal levels.. maybe my eyes are getting old, hard to find such 'intermitent' issue looking at pictures, I think

If you notice the problem only after the tube warm up, you have to look around the tube, using a magnifier to look at solder joints (while slightly move parts) can help you find it. May be just some dirt in the tube socket..

Note: I didn't take a look at the schematic but seeing that 450V capacitor on your picture makes me think of safety concern, please be sure to know about discharging capacitors as they could store enough current to hurt you, even with the amplifier not connected in the outlet.
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Old 9th April 2019, 03:26 AM   #8
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by vooltool View Post

The preamp is not young, around 12 years old, but i use it seldom. I had supposed, may be electric capacitors have dried, and i have changed all of them. It didn't help.


Thanks in advance!
Things that go with age are electrolytics and valves.
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