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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 22nd May 2020, 11:50 am   #1
jascha
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Default Studer / Revox etc BiPolar PROMS! Question and concerns!

Hi everyone,

Hope you're all keeping well.
I would like to scratch the surface on a concern that cropped up in my head regarding so many (now) vintage machines that use discreet components.

I refer to Studer A807 (and many others I understand) that on both Spooling and Capstan boards use Commutation ICs (3 in total).
Finding bin files for eproms has not been so tricky however these commutation ICs, if they go faulty, what can be done to have them replaced?

Touch wood so far they have not failed on me but I'd like to have some backup plan ahead in case either mine (or someone else's machine) needs a replacement of these ICs. On the Studer A807 the part numbers are 1.727.343.20 (ICs 15 & 18 on the Spooling board) and 1.727.331.20 IC 9 (Capstan Board).
Other machines must have their own programmed ICs dedicated just for that model.

I am told that these would need old obsolete programmers that are hard to find and also these ICs might not be so easy to find. It's worth having a bank of data for all these machines if anyone can backup the data from these ICs.

Anyone can shed some light on the subject please so we can help each other protect these machines in case one of us is unlucky?

Thanks everyone
J
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Old 23rd May 2020, 4:45 am   #2
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

I've got some thoughts on the subject although have never actually tried this so it's academic at best. I do have a bit of experience with EPROMs, having used them not only for data storage but also for function mapping in the same way that they are used in certain tape recorders.

Although bipolar PROMs are rare as are the programmers that program them, I'm thinking that it should be possible to replace them, electrically at least, with slightly more modern UV erasable EPROMs (such as the 2716), EEPROMs (Electrcially Erasable PROMs) (such as the 2816), or even Flash (electrically erasable) ROMs.Programmers for these types of chips are still readily available, as EPROM technology was popular in microcomputer systems, so many hobbyists would have had an EPROM programmer for their own projects. In fact, I think it's still possible to buy USB EPROM programmers new today. In contrast, bipolar PROMs would have been used mostly in an industrial context.

A ROM basically is a map from one set of binary values (the address) to another (the data), and the underlying technology is not important, especially in a tape recorder where the access time (which is usually faster for bipolar PROMs than for EPROMs) is not critical.

The disadvantage when using EPROMs is that they are usually physically larger devices (24, 28 and 32 pin devices in 0.6" wide body packages, rather than the typically 16 pin 0.3" wide body packages typically used for bipolar EPROMs), being able to hold much more data - a typical bipolar PROM has 8 address lines (256 addresses) whereas the smallest modern EPROM which uses 5V-only supplies is the 2716 which has 2048 addresses). So some form of adapter needs to be devised. I'm thinking of something along the lines of a 16 pin header which plugs into the socket where the PROM was mounted, emanating at an adapter board on which the EPROM is socketted.

The difference in memory size isn't a problem per se, it's just a question of programming the relevant part of the memory chip, and connecting the unused address lines to 0V.

Well, at least some thoughts on the subject.
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Old 23rd May 2020, 5:01 am   #3
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Smile Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Thatís excellent and thanks for the technical explanation. Usb eprom programmers are infact easily available and I recently bought a TL866 II plus programmer not only to reprogram the Eproms in the A807 but also to test common type 74 LS and HC chips after my machine developed a fault and a headache to fix the problem (due to a short caused whilst working on it).

An adapter might not be too difficult to design as long as each pin corresponds to each other on both chips ( pin 1 to pin 1 and so on). Programming an eprom from a prom file will need an expert like you to come up with a conversion file I would imagine. Would it be something you would look at if I received the backup files for these prom ICs? Eproms are easily available and as long as they can physically fit in the space provided on the boards this really could be a solution for the future!
The question remains as to why Willi Studer decided to design the electronics for so many machines using this technology and not eproms straightaway?
Thanks Ricard
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Old 23rd May 2020, 8:23 am   #4
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Bipolar fusible link PROMs were the original programmable devices, so they were what was available at the time. In fact the common term 'blower' for a programmer dates from that time when the chips really were programmed by blowing internal fuses. Only a handful of modern programmers, very very high end ones which can program absolutely everything else as well, support the programming of Bipolar PROMs.

You can, in most cases, substitute a bipolar PROM with an EPROM programmed with the code and rearranged into the correct pinout with an adaptor. It's messy but it works. Usually the EPROM device will be a wide-bodied 24 or 28 pin device, whereas the PROM will typically be a 14 to 18 pin narrow bodied device.

There is one caveat: Sometimes bipolar PROMs were chosen because of their speed, generally considerably faster than EPROMs of the same period. For example, you will find them used in video pattern generators for this reason. In cases like this you may not be able to use an EPROM as a substitute.

If you have a specific job in mind, I and probably a few others here have 'vintage' high end programmers which can read and program most, but not all, of the 1970s-1990s bipolar PROM devices.

If you can provide original programmed devices for me to read and blank ones to copy them into, I don't mind doing that on a limited basis for no cost, so say if you have a machine which has three such PROMs and you want them read, file copies of the contents made and backed up and spare blanks provided by you programmed, I'd be happy to do that on a one-off basis. I wouldn't want to start doing it on an industrial scale though.
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Old 23rd May 2020, 9:57 am   #5
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

A couple of points, although I don't have such a tape recorder myself....

Years ago I read a piece of advice on motoring (sorry Mods). Which was (back then) to carry some basic spare parts. The idea was that you are much more likely to be able to find somebody who knows what is needed and can fit it that somebody who knows what's needed, can fit it _and has the part.

In the case of these tape recorders (and other things using bipolar PROMs) you are much more likely to be able to find a blank and a friend with a programmer than a blank, a friend with a programmer who also has a listing of the data to put into the PROM. So it is worth making a 'dump' of the data.

You don't need a programmer to read out the PROM. All you have to do is set up each combination of 0's and 1's on the address lines and record the states of the data lines. For a small PROM (there's a 32*8 bit one, for example) you can even do it by hand on a breadboard using DIP switches and LEDs. For anything larger it helps to automate things, I suspect something like an Arduino could do it (although this is not my area). Of course this (and reading the chip out with a programmer) depends on getting the IC out of the board without damage. If it's socketed then it's trivial. If it's soldered then it's up to you whether you want to risk damaging the PCB or IC to get a backup. I feel it's a small risk so if I had such a tape recorder I would desolder a PROM.
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Old 23rd May 2020, 10:18 am   #6
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Modern parallel NOR Flash devices like this seem like they would be ideal for replacing bipolar PROMs as even the smallest capacity devices store 2M bytes or so, access times are much faster than EPROM, programmers are easily available and cost is low.
The downside is the awkward fiddly packages such devices come in and that they use 3.3V or 1.8V supplies.

John
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Old 23rd May 2020, 10:39 am   #7
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Wow that’s quite a handful of useful replies and thanks to all for your contributions. This would be beyond my understanding of how these data lines function I’m afraid so it would be more practical for me to backup the IC’s, which thankfully are all socketed on Studers.

@SiriusHardware thank you for your generosity of offering to backup these ICs and would love to take you up for your kind offer. If I may ask if I can come back to you however at a later date please when I can borrow a set of spare ICs from a functioning but neglected machine I would be most grateful. I have access to some machines from a foreign Radio Station back home and since these machines are now out of service I can have access to them to borrow whatever I need from them and then take them back on my return. With the current situation I cannot go there and I’m using both my machines in my UK home on a daily basis. I’m very grateful for this offer and will PM you when I have the opportunity to send you these ICs and a set of blanks please to have them programmed if that’s ok.

Stay safe everyone
Regards
J
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Old 23rd May 2020, 10:50 am   #8
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

In the first instance you would need to let me know what the original devices are so I can tell you whether my programmer actually can program them.

Then you would have to find new, never used blanks because these chips can only be programmed once (old ones pulled from PCBs would be useless, as they would already be programmed).

If we get through both of those hurdles then I would be happy to do that for you.
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Old 23rd May 2020, 11:00 am   #9
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Absolutely correct. I shall do all I can to find out exactly what device they are as the different ICs sit on both Spooling and Capstan Motors. The only thing that I can see in these ICs is a sticker with a Studer part number Iím afraid and I believe they are 16 pin ICs. Would it help if I attach an image from both the schematics? I attach 2 images which show both IC 18 and IC 9 on the 2 different boards.
Once I know what ICs I need I shall buy the blanks . I am told that they are 256 bits if that makes any sense?

Thanks again
J
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Old 23rd May 2020, 11:26 am   #10
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Ah, that's interesting, they appear to be used as encoders.

The first diagram has sufficient detail, combined with the '256 bits' figure, to narrow it down to a number of devices which have that pinout and are compatible with each other in read mode. It looks like it's 8-bit wide, 32 bytes. Something like the Philips / Signetics 82S129 might do to replace that one, I will check the pinout. That would be good news as I actually have some blank 82S129s.

Although the detail in the second diagram is not as good, it appears to be connected in exactly the same way so it's probably exactly the same device or one with a compatible pinout, but probably programmed differently. I'm guessing your chips have an adhesive label on them, the only way to definitely know the chip part number would be to look under the label.

As Tony rightly guessed you can use an Arduino to read the contents of PROMs like this and I already have an Arduino sketch (program) written for that purpose which I can easily modify to work with a 32-byte device, so if you have an Arduino UNO and you know how to load code into it, let me know.

Tony's 'do it by hand with switches and LEDs' method is equally valid for a small 32-byte device lke this, just a bit slower. I wouldn't want to do it that way for a 256-byte or 512-byte PROM though.
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Old 23rd May 2020, 11:33 am   #11
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

No, not pin compatible with the 82S129, that's a pity. False memory, the 82S129 is actually a 256 * 4 bit device. Tony? Any idea what those are or what they could be replaced with from the pinout in Jascha's first image?

Last edited by SiriusHardware; 23rd May 2020 at 11:43 am.
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Old 23rd May 2020, 11:51 am   #12
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

https://www.mikesarcade.com/cgi-bin/...ge=PromRef.txt

Code:
Bipolar PROMs
-------------

32*8
   +------+
O1 |1   16| Vcc
O2 |2   15| CE/
O3 |3   14| A4
O4 |4   13| A3
O5 |5   12| A2
O6 |6   11| A1
O7 |7   10| A0
GND|8    9| O8
   +------+
   Signetics     MMI     TI       Harris  Raytheon  AMD      National  Intel
   ---------     ---     --       ------  --------  ---      --------  -----
TS 82S123 (50ns) 6331-1  18S030   7603-5  -         -        -         -
   82S123A(25ns) 63S081  -        -       -         27S19AC  74S288    -

   Intersil      Fujitsu
   --------      -------
   IM5610        7051
Cheers
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Old 23rd May 2020, 11:56 am   #13
SiriusHardware
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Good man!

I also found a similar list when seems to suggest that the

Philips / Signetics 82S23
AMD 27S18
National Semiconductor DM74S188

..Have the same pinout as well. If so there's quite a bit of choice for replacement devices.
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Old 23rd May 2020, 12:03 pm   #14
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Quote:
Philips / Signetics 82S23
AMD 27S18
National Semiconductor DM74S188
Be aware - those are all open collector versions.

Cheers
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Old 23rd May 2020, 12:16 pm   #15
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Ah, good spot, I didn't see that. Have you noticed, in both diagrams the outputs appear to have pull up resistors on them, so they may actually be open collector output types?
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Old 23rd May 2020, 12:26 pm   #16
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

The pullups are only on the outputs which drive the pnp transistors - I imagine they're just to make sure they turn off completely.

TTL outputs don't go very close to the 5v rail without them

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Old 23rd May 2020, 12:29 pm   #17
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

OK. If jascha can state what the original device types are, we'll be in the best position to help. For the record, I can program all of the types mentioned so far, so that's one problem less to solve.
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Old 23rd May 2020, 12:46 pm   #18
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Hi Guys,

I have taken some photos of both circuits of the Spooling and Capstan motor controls and a photo of the general layout of the capstan motor control. The ICs in question are IC 9 on the Capstan Motor control and IC 15 & 18 on the other board.

At some point I try to carefully lift off the stickers on the ICs that might be covering the print on the original blanks if that might help.

Thank you so much to all and hope this information helps.

Iím very grateful
J
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Old 23rd May 2020, 1:04 pm   #19
SiriusHardware
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

Not your fault, but the forum engine downsizes all images uploaded to it to 800 * 600 maximum so the details on your last images are almost unreadably small. I can see enough to see most / all of the PROMs are wired up more or less the same way and so are likely to be the same device or pin compatible devices.

It looks like you have the service manual there, if you have a parts list what is the full description of the part number(s) for the PROM(s)?
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Old 23rd May 2020, 1:28 pm   #20
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Default Re: Studer / Revox etc BiPolar PROMS! Question and concerns!

IIRC there is a totem pole version of the 74S188. According to my 1983 Texas Bipolar Memory Databook it _was_ the 74S288, renumbered to TBP18S030 (the TBP18SA030 is the 74S188 open-collector version).

Other numbers (looking down the equvalents lists) :

AMD : 27S19
Harris : 7603
MMI : 6331-1
National :74S288
Signetics : 82S123

Note that these devices are all compatible in _read mode_, that is once correctly programmed they should all work in the Revox. But they need different programming algorithms, so not all programmers can handle all makes of PROM.

Assuming Siriushardware's programmer links to a PC (and is not just a stand-alone thing) I think it would be worth making a copy of the PROM as a file (Intel Hex or similar) on said PCB. Even if you don't have a blank now to burn a replacement device, that file could be used in the future.
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