-
Get involved.
We want your input!
Apply for Membership and join the conversations about everything related to broadcasting.
After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
If you use a disposable or false email address, your registration will be rejected.
After your membership is approved, please take a minute to tell us a little bit about yourself.
https://www.radiodiscussions.com/forums/introduce-yourself.1088/
Thanks in advance and have fun!
RadioDiscussions Administrators
Texar Audio Prisms
- Thread starter RadioMan203
- Start date
Parasound said:
Unfortunately I don't have one of those, but I have my trusty old solder sucker and iron. I guess I'll just have to proceed with caution and hopefully not ruin any of the board traces.
A low power iron and a slurper will work fine on them. I've removed and replaced on them without problems.
Good to hear, as I am in the process of ordering new caps and vactrols to refurb the units.
I figured I'd let folks know how I'm making out so far. I'm still on the hunt for the schematic for the MB1 motherboard that reflects production of the pre-500 serial numbered units. Per a fellow poster's suggestion I email Mooretronix but unfortunately he's either missing in action or just not interested in helping me help out the school I'm rebuilding these for. I was hoping to confirm that the alignment procedure posted for the M101's is compatible for the M102s but after several email inquiries I've given up on Mooretronix.
I'm also still on the hunt for the control covers as well.
I'm also still on the hunt for the control covers as well.
What you want is the looseleaf three binder manual, which had a pretty complete set of schematics covering the units with M100 cards. I believe I gave mine to someone and didn't get it back. The control covers are long gone. I have S/n 76 and 78, written on the chassis in magic marker.
Hi Bill,
I have the complete manual for the Texars from 1982... including the M-100 schematics and parts list. In fact, it is a "preliminary" user's manual! Email me off list with an address and I can send you a copy of it. The actual Prisms have long since been sold, but found this lurking in my filing cabinet.
I have the complete manual for the Texars from 1982... including the M-100 schematics and parts list. In fact, it is a "preliminary" user's manual! Email me off list with an address and I can send you a copy of it. The actual Prisms have long since been sold, but found this lurking in my filing cabinet.
Wow, littlejohn. Those are the earliest units I heard of out in the field. The ones we have are 398 and 399 (written on the inside chassis but with serial number stickers on the outside of the units), which may be why they had the M102 cards installed. If you want once I gather my information pool I can send you a copy for your files if you'd like.
I just shot WNTI off an email which may be the help for getting the schematic for the earlier MB1 main board. I think I will have enough info between fellow engineers and this forum to refurb them with new caps and vactrols and put these back into service.
I just shot WNTI off an email which may be the help for getting the schematic for the earlier MB1 main board. I think I will have enough info between fellow engineers and this forum to refurb them with new caps and vactrols and put these back into service.
We had them on all the Katz FMs. Glen had been travelling around with the snakeoil salesman who had the automatiuon setup using (I think) Grundig cassette machines. They'd put on a dog n pony show in a motel room for potential buyers. We all passed pn the automation setup, but loved the Prisms. This was long before the RCF made its debut, you hadda set up your optimod with essentially a vernier on the clipping control, it's range was suddenly reduce to about five degrees of arc by the prism's action. When you had them and nobody else in the market had them, you ruled. This was in the midst of the famous 'loud wars'. If you had a pair of prisms, an 8100 Optimod, and a cp=803 you were unbeatable.
The newer ones would take a higher input level before they came unstuck, about 0dBm was the limit on the old ones. The 102 boards were supposed to replace both the 100 and the 101s,m with a switch to decide which one it was mimicing.
And, I'm sure the gent Glen was travelling with was a nice guy. But her sure came across like a hard sell. Al at AutoHook bought one of the systems, and was not particularly pleased with it. The idea was good, but the hardware (Commodore 64 and the cassette machines) just wasn't quite up to it.
The newer ones would take a higher input level before they came unstuck, about 0dBm was the limit on the old ones. The 102 boards were supposed to replace both the 100 and the 101s,m with a switch to decide which one it was mimicing.
And, I'm sure the gent Glen was travelling with was a nice guy. But her sure came across like a hard sell. Al at AutoHook bought one of the systems, and was not particularly pleased with it. The idea was good, but the hardware (Commodore 64 and the cassette machines) just wasn't quite up to it.
G
Glen Clark
Guest
Hi Guys!
John Kesler from Emmis suggested that I sign in and answer a few questions on this thread. It's been 20 years since we sold TEXAR to Gentner and I am working from memory here. So, if I reference a white test point and it was really blue, I hope people will understand.
As the group had observed, there was a major rework of all of the PC boards somewhere about serial number 500. I don't remember exact;y what the cut-over number was. Also, there may have been a dozen or so boards that had the new M-101 and MB-2 cards but still had the CX-1 and DB-1 boards. The CX (control) board and the DB (display board) had to change at the same
time. And the M-101 and the MB (motherboard) had to change as a pair. But there was no reason that the new motherboard and the old CX board would not work together.
Changes:
CX-1 to CX-2 > added a "bypass" mode so that you didn't have to patch the units out to run the pink noise generator (you remember patch cords don't you?). Also added the 4 feeds to the display board which feed the front panel test points. Lastly, made the feed for the AMC-1 or AMC-2 (AM smart clipper) a 5-pin Samtec socket. On the CX-1, the cable to the smart clipper (if you had an AM unit) was hard-soldered to the CX-1.
DB-1 to DB-2 > added the colored test points and a TL084 as an isolation amp to drive them.
MB-1 to MB-2 > biggest change was to run two ground returns from the four M-100 (M-101) sockets, one for analog, one for digital. The MB-1 had a common ground for both and there was a lot of digital hash from the National LM3914 bar graph driver chips that was contaminating the analog signal. Running separate ground made the noise floor lower. Another change was to make the feed to the PR-1 phase rotators from a 5-pin socket. In the MB-1, the PR-1 pigtail was hard soldered.
M-100 to M-101 > changed the dot graph to a bar graph
M-101 to M-102 > this was done by Gentner. My understanding is that it was mostly for thermal stability. The linear-to antilog convertor (2N3904) had to stay exactly on the correct point on the knee of the curve to work properly. We used a 1N914 (or 1N4148) diode junction to do that on the M-100 and M-101. And while it was another P-N junction and did react to the summer-versus-winter problem, the two junctions were not physically in contact. They did not track as well as they could have. Gentner replaced the 2N3904 with a matched pair. I think is was an MAT-02 or something similar. The M-102 is a better board mostly because of the thermal stability.
By the way, I will be on the panel at the AES in SF this coming Friday at 3 PM. I will have the original, hand-wired prototype M-100 with me if anyone wants to see it.
PS-1 to PS-2 > On the PS-1, both heat sinks for the 7815 and 7915 were up in the air. On the PS-2, we laid the positive heat sink on the board for better heat evacuation. The current on the
positive rail was a lot more than on the negative rail due to the fact the LEDs all came off of the positive rail. When we went to the bar graph and the higher current, the PS-1 could not handle the additional current. The heat rise on the 7815 was too much. A PS-1 is fine for a dot-graph prism (M-100 and MB-2). But the bar graph prism requires the PS-2.
One other thing about the power supply. The original transformer was an LP-30-340 (30 volts and 340 milliamps), which worked fine when you had decent line voltage. But a lot of mountaintop sites had low line voltage and the 7815s would fall out of regulation and the SNR would go crazy. We changed the transformer to an LP-34-300, which gave a higher DC voltage at the input to the 7815. The later problem was that 300 milliamps was not enough to feed the AMC-2 AM NRSC smart clipper, which came along 2 years later. The AMC-2 had a lot more op-amps in it than did the AMC-1. We had a company in State College, PA custom-wind some LP-34-340s for us, which really saturated the core and made it hot. But it was all within ratings. Gentner replaced the "flat pack" transformer with a torroid, which was a better solution.
Miscellaneous: The specified attenuator was a VTL2C3, not VTL5C3, although the difference between the two is slight.
I concur with the group. The best thing to do is shotgun all 5 electrolytics on each of the 4 M-101 boards. After 20 years, the paste is probably pretty dry. I have seen many dead or limping Prisms come back to life simply by replacing these caps. The guy who made the automation machines from the DAT tape decks was Steve Bellinger of Decatur, Illinois. He also owned WDZ(AM). His company was called Systemation. The software was slick - way ahead of its time. But, as the group observed, the mechanical construction of the tape decks did not hold up well to 24/7 operation.
I hope that helps. If any one has a specific question, I'll try to watch this board for a while. Or, feel from to email me at glen_at_clarkcom.com (one "n" in glen).
With best regards,
- Glen
John Kesler from Emmis suggested that I sign in and answer a few questions on this thread. It's been 20 years since we sold TEXAR to Gentner and I am working from memory here. So, if I reference a white test point and it was really blue, I hope people will understand.
As the group had observed, there was a major rework of all of the PC boards somewhere about serial number 500. I don't remember exact;y what the cut-over number was. Also, there may have been a dozen or so boards that had the new M-101 and MB-2 cards but still had the CX-1 and DB-1 boards. The CX (control) board and the DB (display board) had to change at the same
time. And the M-101 and the MB (motherboard) had to change as a pair. But there was no reason that the new motherboard and the old CX board would not work together.
Changes:
CX-1 to CX-2 > added a "bypass" mode so that you didn't have to patch the units out to run the pink noise generator (you remember patch cords don't you?). Also added the 4 feeds to the display board which feed the front panel test points. Lastly, made the feed for the AMC-1 or AMC-2 (AM smart clipper) a 5-pin Samtec socket. On the CX-1, the cable to the smart clipper (if you had an AM unit) was hard-soldered to the CX-1.
DB-1 to DB-2 > added the colored test points and a TL084 as an isolation amp to drive them.
MB-1 to MB-2 > biggest change was to run two ground returns from the four M-100 (M-101) sockets, one for analog, one for digital. The MB-1 had a common ground for both and there was a lot of digital hash from the National LM3914 bar graph driver chips that was contaminating the analog signal. Running separate ground made the noise floor lower. Another change was to make the feed to the PR-1 phase rotators from a 5-pin socket. In the MB-1, the PR-1 pigtail was hard soldered.
M-100 to M-101 > changed the dot graph to a bar graph
M-101 to M-102 > this was done by Gentner. My understanding is that it was mostly for thermal stability. The linear-to antilog convertor (2N3904) had to stay exactly on the correct point on the knee of the curve to work properly. We used a 1N914 (or 1N4148) diode junction to do that on the M-100 and M-101. And while it was another P-N junction and did react to the summer-versus-winter problem, the two junctions were not physically in contact. They did not track as well as they could have. Gentner replaced the 2N3904 with a matched pair. I think is was an MAT-02 or something similar. The M-102 is a better board mostly because of the thermal stability.
By the way, I will be on the panel at the AES in SF this coming Friday at 3 PM. I will have the original, hand-wired prototype M-100 with me if anyone wants to see it.
PS-1 to PS-2 > On the PS-1, both heat sinks for the 7815 and 7915 were up in the air. On the PS-2, we laid the positive heat sink on the board for better heat evacuation. The current on the
positive rail was a lot more than on the negative rail due to the fact the LEDs all came off of the positive rail. When we went to the bar graph and the higher current, the PS-1 could not handle the additional current. The heat rise on the 7815 was too much. A PS-1 is fine for a dot-graph prism (M-100 and MB-2). But the bar graph prism requires the PS-2.
One other thing about the power supply. The original transformer was an LP-30-340 (30 volts and 340 milliamps), which worked fine when you had decent line voltage. But a lot of mountaintop sites had low line voltage and the 7815s would fall out of regulation and the SNR would go crazy. We changed the transformer to an LP-34-300, which gave a higher DC voltage at the input to the 7815. The later problem was that 300 milliamps was not enough to feed the AMC-2 AM NRSC smart clipper, which came along 2 years later. The AMC-2 had a lot more op-amps in it than did the AMC-1. We had a company in State College, PA custom-wind some LP-34-340s for us, which really saturated the core and made it hot. But it was all within ratings. Gentner replaced the "flat pack" transformer with a torroid, which was a better solution.
Miscellaneous: The specified attenuator was a VTL2C3, not VTL5C3, although the difference between the two is slight.
I concur with the group. The best thing to do is shotgun all 5 electrolytics on each of the 4 M-101 boards. After 20 years, the paste is probably pretty dry. I have seen many dead or limping Prisms come back to life simply by replacing these caps. The guy who made the automation machines from the DAT tape decks was Steve Bellinger of Decatur, Illinois. He also owned WDZ(AM). His company was called Systemation. The software was slick - way ahead of its time. But, as the group observed, the mechanical construction of the tape decks did not hold up well to 24/7 operation.
I hope that helps. If any one has a specific question, I'll try to watch this board for a while. Or, feel from to email me at glen_at_clarkcom.com (one "n" in glen).
With best regards,
- Glen
Great info, Glen. It appears the Prisms I have are either from the later end of the Texar run or were perhaps refurbed by Gentner as it seems to contain a hybrid of updates such as the PS-2 and M-102 cards even though both of my units have the original MB-1 while my DB-1 does have colored test points. With serial numbers in the late 300 series I wonder if this was near the transition.
The thing that is odd was while the notes I've been able to unearth with the assistance of fellow engineers the vactrols specified both the 5c3 (for the M102) and 2c3 (on the Texar MB-2). Both my MB-1 boards also have 5c3's as well, so I wonder if this was a short production change or due to a parts shortage. I just purchased a supply of 5c3 vactrols as I have had several folks say these devices do indeed age over time - how true this is has yet to be determined. If I can cull together enough info to realign the M102 cards I will replace the old vactrols.
Thanks for popping in, Glen. If you should think of anything that will benefit my rehab for the school station's units please feel free to chime in.
The thing that is odd was while the notes I've been able to unearth with the assistance of fellow engineers the vactrols specified both the 5c3 (for the M102) and 2c3 (on the Texar MB-2). Both my MB-1 boards also have 5c3's as well, so I wonder if this was a short production change or due to a parts shortage. I just purchased a supply of 5c3 vactrols as I have had several folks say these devices do indeed age over time - how true this is has yet to be determined. If I can cull together enough info to realign the M102 cards I will replace the old vactrols.
Thanks for popping in, Glen. If you should think of anything that will benefit my rehab for the school station's units please feel free to chime in.
Personally I just think it's great how the community helps out one another. Sometimes we're the ones sharing, other times we're the ones in need of assistance. It works out pretty good either way. Having some great resources available like Glen, Bob, Frank, Cornelius, etc is the icing on the cake.
I must say,
It was cool to see Glen chime in on his old baby
. Glen is a cool guy. He is definitely one of those folks whose work has inspired me and a few others to come up with unique AGC designs!
Hope he hangs about more often as Audio Prism discussions are a favorite pastime for folks on this board!
Welcome, Glen!
-Cornelius
It was cool to see Glen chime in on his old baby
. Glen is a cool guy. He is definitely one of those folks whose work has inspired me and a few others to come up with unique AGC designs!Hope he hangs about more often as Audio Prism discussions are a favorite pastime for folks on this board!
Welcome, Glen!
-Cornelius
Glad to see yas, Glen. What ever came of Bellinger? I had forgot his name and Systemation. And you're right, the thing would of done well if it had of had decent transports. Nobody ever made a decently rugged cassette machine. ITXC showed a nice prototype one NAB, but never went to production. And wouldn't sell me the prototypes, either.
'3320Tango, say altitude'
'altitude'
'3320Tango, say altitude'
'altitude'
SO I am almost 4 years late to this discussion. I met Glen in the mid 80s and bought SN 10/11 from the back of his Datsun. I was really interested in his antenna software much more than the audio processing that came with the ride. We developed a long term respect on several levels and I went on placing Audio Prisms all over the planet for Glen.
F
fugazi
Guest
I have about 10 new vactrec cells in order to renew the Audioprisms.
Someone interrested?
BR
Evert
Someone interrested?
BR
Evert
- Status