[Dillen]

A capacitor problem, perhaps.
Check the 7Vref to the Dolby ICs.
Does the VUs still deflect or will they fall to zero as sound disappears?

Martin

[jbh2]

Hi all.

Got new belts, good cleaning and new LEDs in display. Very small LEDs.
When playback it only play for approx. 1 sek, then no sound at all in both channels.
Then REWIND for 3-4 seconds and then it can play again but only 1 sek.

Tried other tapes, same result.

Record is OK.

Any hints ?

Br Jens

[Dillen]

Sounds like a mechanical problem, – misaligned tapeheads or something bent in the tape path.
Is the tape running off the head?

Martin

[jbh2]

Hi Martin.

I will check the 7v ref. But Dolby is OFF.
Yes the VU follow the sound.

If I gently touch the pins on tapehead, L and R, with my screwdriver I get 50 Hz hum i both.
Very clear, steady and strong signal. No dropout in hum.

[Dillen]

Did you check the 7Vref?
It’s not important if Dolby is in or out. The signal runs through parts of the Dolby ICs regardless.

Martin

[jbh2]

The Recording is OK. Only one head. Tape is running perfect on head. Only Playback problem..

[jbh2]

No time yet, but will do it soon. Thanks again for fine info,

[Dillen]

So…

Sound drops out after a few seconds, and VU-meters follow?
The tape keeps running?
Both tape reels are rotating?
And if you touch the tapehead solder tags you get a buzz from the speakers and deflection on the VU-meter?

Sure the tape has a good recording on it?

Martin

[jbh2]

Result of checking the 7 volt. Both L and R were 6,89 Volt and the 14 volt is 13,8 Volt.

So I think thats fine. But again, with 50 hz hum on the tapehead, I get fine signal in both channels as long as I will.
Is it possible to connect a sinus signal from a tonegenerator at the tapehead. (input on playback amplifier)

Or do you have any other suggestions I would be happy ?

Thanks again Martin.

 

[jbh2]

yes to all.
I will try to find another tape, and also have another tapedeck (working) and will make a new recording on that.

Will a bad/very old tape have that performance, sounds OK a short time, then silence. ?

[jbh2]

Finally, its a winner, thanks to you Martin.

I got the HK2500 tapedeck up and running. Just new belts then OK. Then I tried my testtape in it, and the tape was full of dropouts, and very bad overall.
Then tested a lot of my old tapes and most of them had dropouts.
(Old tapes loose their megnetism)
But found 2 good ones (99 % good) and gave them to B&O 8004.
Holy moses, it worked. ! Both channels, VU, dolby in/out, timerdisplay. All fine.

(until now, maybe some details isnt working, but so far so good)

So you were right Martin and I was getting “blind” and forgot the testtape, and only focused on the 8004.
Thanks for keeping your interest and continued help. Very grateful and happy.

 

[Author]

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