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Tape Deck Control Board
This board came with an additional DIY board that had been patched into it
Turns out this add on board is to change the momentary Pause function to a latching pause function
I didnt like this bodge up so I disconnected it.
Turns out you can actually get a plug in board that does the same thing from Revox online so I have ordered one of them, looks a much more professional option
https://www.revox-online-shop.com/zu...pause-77-r0023
https://live.staticflickr.com/7884/3...b748ed8b_c.jpgIMG_2246 by Alan Towell, on Flickr
https://live.staticflickr.com/7887/4...ea6ab2e8_c.jpgIMG_2247 by Alan Towell, on Flickr
https://live.staticflickr.com/7918/4...66ddc343_c.jpgIMG_2253 by Alan Towell, on Flickr
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Been doing some more work on my B77 recently to resolve a few issue’s
I was getting a regular wow from it that I put down to the capstan roller wheel as it was a bit tired but when I got a new one the problem was still there after cleaning the whole tape drive. I thought it might be some oscillation from the capstan drive motor board so I checked out the electrolytics I recapped this board with and they were just general purpose ones from a A77 service kit I bought a while back but they had very low ESR, so I decided to change them back to some new AVX tantalums that I had and this has cured the problem.
https://live.staticflickr.com/65535/...eebde28f_c.jpgCapstan drive board by Alan Towell, on Flickr
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I was never very happy with the corrosion on the main audio switch board so when I seen a decent one come up on ebay for £20 I bought it and switched it over, this board was in very nice condition and had metal film resistors to was a recent version
https://live.staticflickr.com/65535/...0bdf6743_c.jpgBasis boaerd 2 by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...de0ae8b7_c.jpgBasis board 1 by Alan Towell, on Flickr.
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I was also getting some intermittent output fro m the left channel and I traced that to the poor quality RCA sockets which were loose and tarnished.
The RCA plugs on the A77 and B77 are crap and too close together to get the plugs in properly so I bought a set of replacement ones from Revox online in Germany. Fitting was straight forward but yo have to do some work with a round file to accommodate the extra spacing in the new circuit board
I also did away with the 5 pin din radio socket wiring as it was also knackeered.
I changed the 2 output pots for a couple of Sfernice P11S ones I had form a passive pre amp.
This cured the intermittent output so sounding much cleaner now with even channel balance.
Before
https://live.staticflickr.com/65535/...f707f7c7_c.jpgOld in out board by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...191386fd_c.jpgIn out board 2 by Alan Towell, on Flickr
After
https://live.staticflickr.com/65535/...716ca496_c.jpgIn out board by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...0d6dd72f_c.jpgNew RCA Board by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...e8b85b78_c.jpgIMG_2456 by Alan Towell, on Flickr
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My record board didn’t have the muting circuit board so again I picked a one up from ebay and fitted it
Whilst I had everything apart I also changed out all the carbon film resistors directly in the signal path for Takman Rey metal films on the input, record and reproduce boards
https://live.staticflickr.com/65535/...900c9a67_c.jpgMuting circuit board by Alan Towell, on Flickr
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So after all this I calibrated the deck for RTM LPR90 tape and the frequency response form it is within +- 1 db and it sounds really good
Here is a short video of the calibration check after adjustment, input was from an NTI Minirator MR Pro signal generator and the output was monitored with a Leader 186A dual channel AC Voltmeter all set for -10dB
https://www.youtube.com/watch?v=t5GNxtpHkMA
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Just got round to painting the back panel on my B77 when I first got this machine the nextel was not sticky but after a few months it is now? .
So after removing the sticky Nextel coating and a good rub down and de-grease with panel wipe, I gave it 2 coats of Halfords Gray Primer.
The best match I could find for the colour of the front panel was peugeot graphite grey metallic which needs a couple of clear lacquer coat as well.
These aren't the best spray cans but did a half decent job in the end
https://live.staticflickr.com/65535/...2fa3b303_c.jpgIMG_2477 by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...843309fd_c.jpgIMG_2507 by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...cf1f9f34_c.jpgIMG_2512 by Alan Towell, on Flickr
https://live.staticflickr.com/65535/...02c59ae9_c.jpgIMG_2509 by Alan Towell, on Flickr
Alan
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Checking the Frequency response after calibration for RTM LPR90 tape
https://www.youtube.com/watch?v=t5GNxtpHkMA
Alan