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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 19th Mar 2017, 2:55 pm   #1
g0hze snowy
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Default Drake R8E

Hi, are there any learned gents out there familiar with the DRAKE 8E receiver, I recently won one on eBay that had a display problem, it seems to pulse bringing the display bright then it fades slightly, it has had the transformer replaced and the variable voltage plug on its rear cut out, now I was thinking that it might be transformer eddies as this one is of an open construction not enclosed, so I fashioned a copper clad enclosure and installed that, don't think it made any difference.

Drake don't supply diagrams or any help that I have found so far, several gents over the pond undertake repairs but the shipping costs as well as the repair make it BER.

so is there anybody out there that can offer advice etc so I can get this receiver performing as it should, I will add that it seems to perform ok, just the display.
regards
Snowy
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Old 19th Mar 2017, 6:16 pm   #2
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Default Re: Drake R8E

"Transformer eddies' don't sound like a likely cause. Was the transformer replaced because of a fault, or was it to make a 240v radio out of one from the US? Is it the right transformer which has been fitted?

The first step without a service manual is to find the outputs of the power supply, and to measure the voltages. Do any of them fade lower at the time the display fades?

David
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Old 19th Mar 2017, 6:36 pm   #3
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Default Re: Drake R8E

http://jvgavila.com/man_ham/r8/R8_R8E-Servicemanual.pdf

Any use?

Lawrence.
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Old 19th Mar 2017, 7:28 pm   #4
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Default Re: Drake R8E

That's the right manual and the set looks quite good quality, if a little old-school nowadays.

Good old 2N5109 as the RF preamp which is a very suitable choice.
SBL-3 diode ring passive mixer
J310 grounded gate FET as IF first stage/mixer termination then two dual-pole 45MHz monolithic crystal filters (prob 15kHz wide)
I'm a bit less keen on a dual gate MOSFET for the next IF stage.
Now it gets interesting! Dual diode ring mixers between quadrature hybrids to do an image-reject mix down to a surprisingly low IF at 50kHz
The synthesiser is a multi-loop design, without using a DDS. At lest it's not a single-loop frac-N.

Overall, very much worth fixing

David
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Old 19th Mar 2017, 7:29 pm   #5
g0hze snowy
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Default Re: Drake R8E

Hi David/Lawrence, I can't say why the transformer was replaced as it was changed before my ownership, when I placed a copper shield around the transformer the display problem seemed to ease, maybe wishful thinking!.
A 12v 3.3amp transformer has been fitted, is that the correct rating for it?.
outputs from the transformer seem to be correct ie: 12v ac out to the board.
Thanks for your input Lawrence, Paula had supplied me why the same details just moments before, it has a schematic so I will be able test the various voltages around the supply and to the VFD , thanks, snowy
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Old 20th Mar 2017, 3:54 pm   #6
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Default Re: Drake R8E

Hi All, well I managed to investigate the display PCB, found pin 4 on j102 was dry jointed, this is the input voltage ( 11 - 16v actually 14.6v), replaced the 1mf cap on the board, still the same problem, all voltages that I can check seem to be ok. Did find 1 x PCB was loose on its mounting posts, so that was sorted but still no improvement, work ongoing. cheers, snowy
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Old 20th Mar 2017, 6:21 pm   #7
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Default Re: Drake R8E

It's LCD, so I guess its the back-light that is fluctuating?
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Old 20th Mar 2017, 6:33 pm   #8
g0hze snowy
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Default Re: Drake R8E

Hi, thanks for your reply, I'm afraid it is worse than that as all the indicators, error, filters, modes, antenna selection logo's all flash randomly, brightness and dim functions all seem to work ok, I have my suspicions about the LCD driver chip, but as I am not professionally trained in electronics, just self taught it is a guess.
Oh I have just spotted where you live, I have an aged Aunty living there, Hawth Park area, cheers, Snowy
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