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 Post subject: BK 707 low reading issue
PostPosted: Sep Mon 06, 2021 5:19 pm 
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Joined: Apr Sun 25, 2021 3:19 pm
Posts: 1
I have a DynaJet 707 that gives low readings on some sockets (#8 and #29 in particular) which are the 12A*7 and the 6L6 test sockets. Have tested all resistors, caps, ensured the lamps are seated properly (not my tester so I'm not ready to solder the bulbs yet).

Tests 6 volt miniatures properly and other 12 volt miniatures fine. Issue seems to be related to these two sockets.

Going to get a sacrificial schematic so I can mark up all common wires to these sockets, but past that I'm stumped.

Any ideas?

Thanks! Tom


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 Post subject: Re: BK 707 low reading issue
PostPosted: Sep Tue 07, 2021 11:23 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11330
Location: Sunbury, Ohio 43074
How low are the low readings, and are you SURE they are not correct? The tubes may be low ;-)

Just because a tube gives a certain reading on tube tester A, does not mean it's going to give the same reading on tube tester B.

A "rough" test would be to buy a brand new 6L6 or 12A*7 and see how they test on the 707

Probably wouldn't hurt to clean those two tube sockets, and make sure the pins aren't loose. If in doubt, replace the sockets.

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 Post subject: Re: BK 707 low reading issue
PostPosted: Sep Tue 07, 2021 5:16 pm 
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Joined: Jan Fri 27, 2017 8:41 pm
Posts: 380
Location: Springwater, NY
Did you measure the heater voltage at those sockets at idle and under test?


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 Post subject: Re: BK 707 low reading issue
PostPosted: Sep Tue 07, 2021 8:14 pm 
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Joined: Feb Sat 20, 2021 3:12 am
Posts: 125
Location: Bryson City, North Carolina
Get you some "interdental brushes" from Amazon and clean the tube sockets well. These things work very well, usually come in 4 different sizes and are not expensive. Use Deoxit (my personal favorite) but I'm sure there's others that would work. Spray a little in the cap and dip the brushes in it. Spray a dab of Deoxit on all the socket rivets. You can use a paper towel under the sockets to prevent it from raining inside the case and wipe out the excess.
Clean all the potentiometers as well. Spray a little into the switch bank and work these as well, I follow that one up with a shot of some fader lube.
Go through the calibration procedure and check all the voltages and as a final check mark up the sockets on the print with the correct voltages and check the socket pin voltages as well.
Soldering the bulbs is not absolutely necessary but it don 't hurt to give ithe sockets a shot of dexoit as well .


Check out the voltages at C4 and C6. If they are old you might think about replacing them

Sorry my keyboard is screwing up. Gotta go figure this thing out.

Edit: A test to see if keyboard is fixed. OK seems to working fine now.

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