Revox B77 REAL time digital counter conversion - part 1 - the mechanicals..

Family_Dog

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Marco, I think you have a wonderful working relationship with that lathe, your tooling is that of a perfectionist!

Glad this came right and that you're happy with the results. Why not just make a youtube video and post the link here?


-F_D
 

marcochezzi

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Family_Dog said:
Marco, I think you have a wonderful working relationship with that lathe, your tooling is that of a perfectionist!

Glad this came right and that you're happy with the results. Why not just make a youtube video and post the link here?


-F_D

I'm almost too embarrassed to say I do not know how.. genuine..  :facepalm:
 

marcochezzi

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Ok so after machining a sensor plate to house the 2 optical sensors I realised I had taken no pics...

Anyway, no biggie, the single most important thing is that it works, the 2 sensors combined create the count pulse stream ,and also the direction indicator (logic switch)

So the display itself is fixed to the chassis, I have temporarily glued it in position, I will be using 3mm cap screws to secure this once I get over my desire to not go out there in the blue yonder....

wJ9JNoP.jpg


The without any cover plate made up yet this is what we see from a front panel perspective, the glare of the display quite obvious but expected..

iDLYY3E.jpg


 

marcochezzi

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Next was to create the display cover panel & bezel...

So go figure, if I use the red perspex as a screen cover, the red display glare remains, and looks crap, if however I use the blue perspex plate, the glare is completely gone with a nice visual on the display, so I used the blue...

It is an old piece so fairly scratched, I will get a fresh piece when sanity returns to our neighborhood...


elqiHFz.jpg
 

marcochezzi

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Next was the bezel, here the idea was to keep a rectangular look in keeping with the tape splicer on the right..

I machined the plate, cut out the perspex, and then machined 2 little push buttons, one for reset, one for return to zero..

While I took no pics in this regard, 2 little switches, the flat square surface mount ones like in your tradition gate remote control, were embedded into the front panel directly behind each push button..

I do not have the return to zero logic designed yet, so that will be a future project, need to let some time pass for the sake of my marriage..

The plate will in all probability be blackened in keeping with the rest of the look, but the pushbuttons will remain silver.

The pushbutton diameter is 3mm at its thinnest..


PEwqcPl.jpg



Here the panel mocked up in place..


mVURCKK.jpg



And here the functional item, colour nicely muted.. The bezel itself is only on temporarily, I will probably lift it a mm or 2 before final mounting holes are drilled..


GW3G8Sh.jpg
 

marcochezzi

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and the youtube video...

Hope this works...

https://youtu.be/61sLq8Kmpl4

if not, hope this works...

61sLq8Kmpl4

 

marcochezzi

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Thanks Swindlehurstguy, apologies on the late reply but I was travelling from my garage to the front door, and had to contemplate 4 lockdown roadblocks on the way...

Lathe is no biggie, just a basic made in Taiwan jobbo from the 80's, strong and fairly well built and can do much better than me  :roll:...



yVY3b1m.jpg
 

marcochezzi

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Thank you Swindlehurstguy, yes, I am my own worst enemy, I love working on these machines, I hate the mess they make, I probably clean them 5 times a day when I am working on them, its an OCD thing.. my wastepaper usage will compliment a small forests sacrifice...

But.. there are some dings, however I will mention not mine..!!

And yes, never enough toolholders, but for now I am broke, so no more purchases, maybe...
 

tonband

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First of all: WOW!! Very nice job!!!!

I wanted to -- and still want to -- do something similar ;-)

A first question:
Could you tell something about the precision of the digital counter? Say, at time h:mm:ss a new song on the tape starts. Now, you play some minutes, then go fast forward, play and then fast rewind again etc. and eventually you reach again to the same time counter h:mm:ss: Does h:mm:ss still correspond to the beginning of the song, or is it "late" or "too early" by some seconds?

Thanks and cheers from Switzerland


 

marcochezzi

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tonband said:
First of all: WOW!! Very nice job!!!!

I wanted to -- and still want to -- do something similar ;-)

A first question:
Could you tell something about the precision of the digital counter? Say, at time h:mm:ss a new song on the tape starts. Now, you play some minutes, then go fast forward, play and then fast rewind again etc. and eventually you reach again to the same time counter h:mm:ss: Does h:mm:ss still correspond to the beginning of the song, or is it "late" or "too early" by some seconds?

Thanks and cheers from Switzerland

Hello Tonband

The time is very accurate, the only time you might ?lose? lose time is if the encoder wheel stops spinning because of bad bearings or air cushion between itself and the tape on FFRR or reel..

The trick is getting correct tape tension on the encoder wheel..

I have seen recently that there is a chap from Germany (??) who has designed a reel time counter for the b77 that does not rely on an encoder wheel for timing, it still uses the belt from the take up spindle, somehow he has worked out the software to make this thing keep time dependent on tape thickness which you preprogrammed, I think it is brilliant, but want to see it work.....
 

tonband

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marcochezzi said:
Hello Tonband

The time is very accurate, the only time you might ?lose? lose time is if the encoder wheel stops spinning because of bad bearings or air cushion between itself and the tape on FFRR or reel..

The trick is getting correct tape tension on the encoder wheel..

I have seen recently that there is a chap from Germany (??) who has designed a reel time counter for the b77 that does not rely on an encoder wheel for timing, it still uses the belt from the take up spindle, somehow he has worked out the software to make this thing keep time dependent on tape thickness which you preprogrammed, I think it is brilliant, but want to see it work.....

Good to know, thanks.


And yes, I heard about that german guy as well, https://www.beis.de/Elektronik/TS1000/RVx-Cnt.html. But, I prefer doing it your way... seems to be more accurate than doing all that calculations...

What kind of sensors did you use for detecting speed and direction? Hall effect or optical?

And what kind of microntroller did you use to process the impulses you get from the sensors?

Thanks again,
pascal
 

marcochezzi

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Pascal I used 2 optocouplers 90 degree out of phase as the timing signal source and direction logic switch, basically the same as a rotary encoder. I did not use microprocessors, I used dedicated cmos logic chips and designed the counter around that, including the pulse divider to 1hz.

I have subsequently changed the chips to a much simpler dedicated counter chip after I was informed of them in this forum, but if you are good with microprocessors I am sure you will find a simpler solution, I am useless at microprocessor level.

I am not home today, so I will send you the new chip details when I get home tomorrow if you want to go the old school route..

Best regards- Marco
 
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