| K0IZ |
Rating:  |
2021-12-01 | |
| Classy receiver, worth updating a bit |
Time Owned: more than 12 months. |
I have owned since 1965, 2nd owner. Heavy construction, nice looking receiver. Reasonably stable and sensitive. Calibration accuracy is excellent. Typical single crystal filter from the era, however, so poor skirt selectivity. Have made a number of reversible changes.
1. Changed V9 to AGC diode and AM detector (and deleted noise limiter).
2. Change AVC diode (12AX7) to product detector.
3. Deleted 360K from T5 primary and 56K resistors across primaries of other IF transformers to improve skirt selectivity
4. Added 3rd IF to AGC
5. Modified AGC for delay and hang.
6. Shunted screen resistors for V6 and V8 with 56k resistors to increase IF gain
7. Shunted cathode resistors for V6 and V8 with 100 ohms to increase IF gain.
6. Replace rectifier with two diodes
7. Added little 100/50/25 Khz crystal calibrator board, powered from 6V6 cathode, switched by repurposed LIMITER toggle switch.
8. Replace puny ground wires between oscillator coils with 14 ga wires for much improved mechanical stability.
9. Added CL-70 at fuse for gentle turn-on surge
10. Replaced line cord with 3-wire grounded.
In total these make the receiver a very usable receiver and are completely reversible. |
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| WA7OPY |
Rating: |
2014-02-20 | |
| overrated, good looking |
Time Owned: more than 12 months. |
| I have had this reciever for 20 years but it never worked, I bought it to match the pal 1k and the gpt 750 in the shack. I just got the rig to opperate, But I am not real impressed, I know it is not a R390 or a sp600 but coming from T M C I expected a Little more. The Mil spec parts are not there but thay did use cerramic caps so there were very few bad parts to change out. On my set the 1st I F was not working do to a bad 3.5 mcs xtal. and a very poorly built pentode osc/mixer. It required a compleat allignment that is not hard to do. The bfo is very weak and will be pulled by any signal over s9. The front is easly overloaded, and you have birdys every 3.5 mcs (1st stage mixer osc freq). The i f and r f cans and rf coils are wimpy and suject to movement any bump will make the reciever change freq. The readout is not real good but nether was the sp 600. The tunning is silkly smooth and does have the right speed for easy tunning. It is almost usable on ssb but you have to retune offen. The agc is not as good as many old recievers (the bc 348 is better) I think that T M C was tring to build a cheap reciever that hams could buy in the early 60s and cashed in on there name as a high end military contractor of radio transmitters, As most sets were bought by the military not by hams thay realy blew it. I would rate it as a 300.00 dollar reciever not the 7 to 8 thay bring on @bay. I am glad I fixed it, and it is nice to look at and looks good with the gpt 750...... 73s Phil |
|
| NQ5T |
Rating: |
2013-04-03 | |
| It's a radio Pin-up Girl!! |
Time Owned: more than 12 months. |
I just bought my third GPR-90. There may be better BA receivers (I either own or have owned most of them), and no .. it's no R-390. (Thankfully!). It just a great radio. It wins hands down in anybody's beauty contest.
I've bought them and renovated them and sold them. But I keep coming back to them -- like you're drawn to an ex-girlfriend. Maybe this time I've found the keeper :)
You do need a GSB-1 (or Sherwood Mk-something, or HC-10, or a C-E Slicer) for best SSB performance. But that isn't the point .... |
|
| KG8LB |
Rating: |
2013-04-01 | |
| At the top |
Time Owned: more than 12 months. |
RE: The comment about dial cord stringing by a previous "reviewer" ,W9LBB . Simply put , the GPR 90 HAS NO DIAL CORD ,period . The dial calibration from band edge to edge is near frequency meter accuracy .
Not sure where that reviewer found a National NC-180 for that matter .
I have now owned 6 GPR90 receivers and they have all been beautuifully built , smooth operating receivers .The GPR90 release was in the mid 1950s and for the money , a great receiver . Good audio , outstanding fit and finish , high quality components and excellent wiring/assembly.
The dial calibration is the best I have seen on any receiver that is tuned VIA air variables . The stability ranks tops . A good technician of course realizes that 60 year old receivers are going to need some maintenance . The only "stability" issues I have seen on GPR90 was easily resolved by a good cleaning of the wiper contacts of the tuning caps .
The audio filters are helpful and the crystal filter on a properly aligned GPR90 is very effective indeed .
I have also owned Many Super Pro 600s ,R-390 , R-390A as well as 4 of the very rare R-725 receivers . The GPR 90 is right up there with the best of them and for use on the amateur bands is very convenient and smooth in operation .
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Earlier 5-star review posted by KG8LB on 2008-11-12
I have had the pleasure of owning two of these wonderful receivers now. Not a newcomer, I have owned dozens of boatanchor receivers and this is still on the short list of favorites.
Beautiful fit, finish and highest quality components. Very clean, Mil-spec wiring job and buttery smooth controls. This is a top drawer receiver that takes no back seat to the big "C" stuff.
Seems some folks expect to open a box up, plug in a 55 year old receiver and have it beat the pants off eerything else. You might get lucky..likely not. The GPR-90 works exceedingly well when properly aligned.
To make the most of it's excellent crystal phasing filter you MUST align the IF to the actual filter frequency. With good tubes, clean controls and everything up to spec this is still a very viable receiver even in today's spectrum with it's abundance of slop bucket splatter. The audio from the single ended 6V6 is splendid.
To really add tools to the QRM fighting arsenal pick up the matching GSB-1 SSB adapter. It isn't just for slop-bucket use. The SSB adapter allows for AM reception of either the upper or lower sideband, slicing off the offending interference quite nicely. It also alows to offset the passband with very fine control. The GSB-1 has it's own 6V6 audio amp built in as well.
The receiver is also very STABLE , even after all these years, the calibration is spot on. Complaints regarding "drifting" are often due to a bit of corrosion on the air variable contacts. A little cleaning here and the receiver becomes rock solid.
Had all the big names here but as long as there are tube type receivers in this shack at least one of them will be a GPR-90 .
More fun than any transistor toy radio too! ;-) |
|
| KB8QEN |
Rating: |
2009-06-07 | |
| A GREAT receiver |
Time Owned: more than 12 months. |
Very well made to a standard that Hallicrafters never approached. This is a fine receiver and an excellent example of prime ham equipmeent of the 1950s and 1960s. I did get a kick out of the comments from on of the "experienced" reviewrs who actually replaced his "dial cord" with a steel cable! This radio does not and never did have a dial cable. What is up with that? I guess it explains why he only gave it a 3?
Anyhow the prices on these in the used market makes them a real deal compared to some of the boutique typ receivers that seem to get a lot of attention due in large part to their relative scarcity.
The other 3 rating came from a fellow that claimed when he hit his it would warble and drift. Most operators who are familiar with vintage receivers would realize that a little maintenance is called for. This is generic to any receiver tuned with air variable caps. A little cleaning restores the excellent stability to this receiver.
Along with excellent stability this receiver has extremely good calibration and tracks better than most across the bandspread. It rates easily as one of the best calibrated analog tuned general coverage vac-tube receivers built.
Very well made with high quality components the GPR-90 is a radio De-Luxe for the operator who really knows and appreciates fine receivers.
Sorry fella, no DIAL cord on these! |
|
| WB8UHZ |
Rating: |
2008-11-08 | |
| Great |
Time Owned: more than 12 months. |
I can't believe some of the comments about the GPR90, or maybe I can. I picked one up in 1992, was not impressed. I used it now and then but the selectivity was not good etc. Then I decided what it needs is a good alignment. Guess what, what a fantastic receiver, one of the best in all respects. This is a great receiver and excellent audio.
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Earlier 5-star review posted by WB8UHZ on 2005-09-09
Well built , great audio, needs some improvement in selectivity, but can be adapted, improved... had this one for better than 10 years... get one if you like great older radios. |
|
| W0OGH |
Rating: |
2008-06-08 | |
| Good looking radio |
Time Owned: 6 to 12 months. |
| i bought several of these hoping to find a keeper. Fell in love with them when they first came out back in the late 50's. Thought it was the cats meow. As i said i've had several of these in the past 10 years. None still around. Most annoying was the instability of the radio. bang on the sides of it or on the top and listen to it warble and drift down the band. Visibility: gorgeous radio to look at especially when all lit up in the evening. Always fun to read the manuals. I've got other TMC transmitting equipment that i'm keeping btw. My Collins 388's, 75A-2, Sp-600 and AR-88 are much nicer radios to operate and much more stable. |
|
| W9LBB |
Rating: |
2005-09-20 | |
| An Oldie that's only an OKie |
Time Owned: more than 12 months. |
I had a GPR-90 for about 8 - 10 years and used it quite a bit, mostly on 40 CW and for general SWLing.
Good points:
A Heavy Metal, Old School communications receiver built mainly for the government market. Dependable, and very seldom needed any sort of repairs.
VERY sensitive, and handles big signals well without overloading.
Quite good selectivity, assuming the IF strip has been correctly aligned, allowing the crystal filter to properly be brought into play.
Quite good audio! This one is a winner for AM operation, and especially AM broadcast band DXing.
Probably the BEST S-meter I've ever encountered on a boatanchor receiver. Once calibrated at 50 uv = S9, it tended to stay there for years and years without the need for recalibration. The meter was HONEST, and not "bouncy" like the ones on Hammarlund gear of the same vintage.
Not so good points:
Tuning dials are a bit "springy" due to the stringing technique. I was never able to cure it, even by restringing with steel fishing line. The problem appears to be that the stringing paths are quite long, and span too much distance.
It did OK on SSB, but it would have been much better with the external SSB adaptor.
The radio's frequency was somewhat drifty. For some reason, it never seemed to reach an operating temperature that it liked. It MAY be that becase the cabinet I had it in wasn't the original one temperature control and equilibrium may have been the issue here.
All in all, I found it to be a pretty good receiver, but the SP600, R390 and R390A were better overall; the GPR-90 had them both beat on sensitivity tho. The drifting problem I encountered was about the same as the National NC-170 and NC-180 that I'd had before it. |
|
| W6LBV |
Rating: |
2005-09-10 | |
| "Scenes of my young years grow warm in my mind....." |
Time Owned: more than 12 months. |
I saw the new review of the TMC GPR-90 and couldn't refrain my adding my own. However, I have a slightly different version of the '90, knowledge of which may be useful to some collectors.
My TMC was obtained about fifteen years ago in a sealed-bid surplus property bid sale. As I recall, as high bidder I paid about $25 for it and then swapped out a bad rectifier (vacuum) tube, and it's been receiving without any problems ever since.
The GPR-90 is a "big iron" old-school radio, loaded with vacuum tubes and front panel controls, and it was built in an era when silicon was generally found only in beach sand. It is designed for rack mounting in standard 19" relay racks, is constructed to last "for the ages," and is almost too heavy for one person to lift. It operates solely from 120 volts a.c. It seems quite likely that mine was a sea-going receiver, possibly military but more likely riding aboard a civilian shipping or research vessel.
My radio is a GRP-90RXDS. It differs from the model shown in the photograph above by having provisions for ten quartz (receive) crystals, each providing a single fixed frequency channel. The crystals are located behind a small hinged panel in the (extended) space directly above the main tuning dials and the S-meter. A separate wafer switch, marked "HFO," provides selection of one of the ten crystals or the main VFO. The crystal holder positions in my receiver were fully populated on arrival, and the spot receive frequencies were marked in pencil on a chart located on the swing out cover. But I have not attempted to receive using the crystals. And I have other, more modern LF/MF/HF-capable receivers, leaving this one permanently remaining in my collection solely for enjoyment and nostalgia.
With a random length long wire above the roof, the '90 has exhibited good (noise-limited) sensitivity and it hauls in HF and BCB signals from around the world and the country, respectively. It does have a BFO (but no product detector) and on-board i.f. crystal filters for some selectivity. However, it is not a "modern" receiver incorporating roofing filters and DSP processing, and it cannot be used for reception of Amateur DX contest pileups or for separating two CW signals that are only 150 Hz apart. It also does not have the "top of the field" elegance of R-390s or Collins receivers of that era. But the work that it does, it does quite reliably. If you are interested in "vintage receivers" of an earlier day and have the opportunity to buy one inexpensively, you can have a bit of fun with it and learn something about the history of electronics technology.
My favorite use for the receiver is to listen in the evenings to the BBC World Service Carribean relay on 5975 kc/s (not "kHz," which designation was not yet in use when this receiver was built). With the i.f. selectivity set wide open, the AGC and ANL turned off, and the AF gain fully advanced, I back off the RF gain pot to reach a comfortable listening level. The receiver is connected to an eight inch full range speaker in a good enclosure (the GPR-90 has no internal speaker). Broadcast-quality audio floods my office/shack, sufficiently good to fool my wife once into thinking that she was listening to a local AM radio station.
This was a rugged receiver manufactured for serious commercial purposes. It was never intended to be equivalent to a Grundig or Sony solid-state "all band" consumer portable, nor to equal the performance of a modern Watkins Johnson monitor. But it did its job well, for many years. If you approach it with this understanding and don't bemoan its omission of "modern features" such as, for example, lack of an RS-232 port on the rear panel, it is well worth having. |
|
| WB6MYL |
Rating: |
2005-09-10 | |
| ONLY OK |
Time Owned: more than 12 months. |
| I, too, wanted to like this receiver; anything by TMC has to be high-end for its time? it was a nice looking receiver that had average performance. I didn't think it was that selective or sensitive; did sound very good w/ the TMC 591A SSB adapter but the 390A, Racal RA-10, 51J-4, and SP-600 ran circles around it. It was one of my few receivers I have actually parted with. Regards, Phillip W. Harris, PhD.J.D.P.C. |
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