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Author Topic: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE  (Read 237 times)

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Offline jpb6061

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EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« on: May 09, 2022, 12:58:49 PM »
Hello All,

I've been enjoying working on my Eros Tape Kit and trying to do it slowly and deliberately; really hate to ask for help, especially on my first post, but really appreciate the opportunity of doing so.

The instructions are about the best I've seen in a kit, and the photographs are clear and helpful. I'm sure my mistakes are the result of a combination of age and eyesight, sadly! I like the ongoing test procedures and have come up short by 100 volts at OB/D1 at my current state of assembly.

I have installed and tested the Power Supply board and get 6.3V and 285V outputs.

I installed the Shunt Regulator board and when I tested the wires from the tube socket D1 and D6, D1 is 100V less than D6 which appears to be correct at 223V.

D6  223V                        D1 124V


Here are additional measurements:
AREG 223V                     BREG 124V
IA 284V                          IB 284V
OA 223V                         OB 124V


Any hints on what to look for will be appreciated. 

Regards,

JB



Offline Paul Birkeland

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Re: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« Reply #1 on: May 09, 2022, 01:42:13 PM »
How old is this kit?  The LEDs we provide can't really sit around for years and years and then be soldered safely, as they absorb moisture slowly over time and can be damaged from soldering heat as it purges the moisture quickly.

What are your Kreg voltages?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Birkeland

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Re: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« Reply #2 on: May 10, 2022, 03:52:33 AM »
To add a little more to this, there are wire jumpers that go to the 9 pin socket from the board.  They connect to pins 1, 3, 6, and 8 on that 9 pin socket, and if you swap either the 1 & 6 pair or the 3 & 8 pair you'll get the exact symptoms you're having.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline jpb6061

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Re: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« Reply #3 on: May 10, 2022, 12:26:46 PM »

Thanks Paul,

I double-checked my wiring and the Kreg voltages.

Kreg A    5.383v  (stabilized)

Kreg B    .855v


You're right, the kit is 2017 vintage; I've got a bunch of Otaris in the graveyard trying to make one or two out of five, and a working Teac X2000R (which will probably be my test machine since I don't have any "good" 15 IPS tapes), and a Tascam 32 upon which I've done a minor refurb.  I really enjoy building all kinds of stuff, so decided to work on the Eros for a couple hours at work after 5:00 for relaxation!

JB


Offline Paul Birkeland

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Re: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« Reply #4 on: May 11, 2022, 05:03:32 AM »
The giant mismatch of Kreg voltages would also be consistent with a swapped wire.  It's also possible to accidentally install a 4250 transistor in place of the 431 regulator.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline jpb6061

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Re: EROS TAPE PSU VOLTAGE LOW ON ONE SIDE
« Reply #5 on: May 11, 2022, 12:13:50 PM »
Why yes, you can install a transistor instead of a regulator!  Thanks for pointing that out.  Everything checks out OK for now.

JB