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Post by Deleted on Feb 11, 2013 0:33:26 GMT -5
OK. I repaired the RX and this radio was working well. I noticed the mod LED would illuminate brightly rather easily with the Turner +3B. Also, from day one in 1983, if I turned the pot past 10 o'clock, the radio would squeal viciously. So tonight out of nowhere, the audio seemed to be dropping out. The Mod LED would not illuminate much unless I was close and whistled. So I thought I might have blown Q11 mod limiter or Q12 Mic amp. I go and look at them and they are in the each other's position. Q11 had a 2SC945 instead of a 2SA733 , and Q12 was a 2SA733 instead of a 2SC945. I checked and rechecked. I looked at the schematic www.cbtricks.com/radios/realistic/trc_422a/graphics/trc_422a_sch.pdf. But they showed the reverse. How could this be if the radio was never modded or repaired? Were they put in wrong during production? I may have been unknowingly running a clipped limited with Q11 being reversed and essentially out of the circuit being a NPN instead of a PNP. I swapped the 2 and the radio still worked and now the Turner pot turns all the way with no squeal. I do not know what is going on. My question if anyone has one of these, is please open the lid and give me what transistors are in the Q11 and Q12 positions. Thanks! |
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Sandbagger
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Post by Sandbagger on Feb 11, 2013 7:24:20 GMT -5
OK. I repaired the RX and this radio was working well. I noticed the mod LED would illuminate brightly rather easily with the Turner +3B. Also, from day one in 1983, if I turned the pot past 10 o'clock, the radio would squeal viciously. So tonight out of nowhere, the audio seemed to be dropping out. The Mod LED would not illuminate much unless I was close and whistled. So I thought I might have blown Q11 mod limiter or Q12 Mic amp. I go and look at them and they are in the each other's position. Q11 had a 2SC945 instead of a 2SA733 , and Q12 was a 2SA733 instead of a 2SC945. I checked and rechecked. I looked at the schematic www.cbtricks.com/radios/realistic/trc_422a/graphics/trc_422a_sch.pdf. But they showed the reverse. How could this be if the radio was never modded or repaired? Were they put in wrong during production? I may have been unknowingly running a clipped limited with Q11 being reversed and essentially out of the circuit being a NPN instead of a PNP. I swapped the 2 and the radio still worked and now the Turner pot turns all the way with no squeal. I do not know what is going on. My question if anyone has one of these, is please open the lid and give me what transistors are in the Q11 and Q12 positions. Thanks! That's certainly a strange one, but not completely unreasonable. I worked in a production environment many moons ago, and it was commone for parts to get reversed or for the wrong part to get installed. The people who generally installed the parts weren't engineers, and they just grabbed the parts from their bins and installed them. If the wrong part was accidently put into the bin, most of the time they'd never notice. At least not until the until was put into test. If your radio had an inoperative modulation limiter, it would not have passed the testing, and would have been sent to troubleshoot and repair, where the problem would have been found and corrected. It's also possible that the silkscreen was marked incorrectly. Also, you indicated that the radio was working fine, and the low modulation problem came on suddenly. That would indicate a failed or failing part, and not something that was like that from day one. |
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Post by Deleted on Feb 11, 2013 9:32:30 GMT -5
Ugh! You were right. Silkscreening is way off according to the service manual. The componet jove with the manual location, but not the silk screening. I went to pull the limiter components to measure them, and D17 was clipped! I never clipepd anything. This was only in for service was when I had the Turner wired when I was 16 years old. I am guess that old guy clipped D17 !
To make matter worse, the diode went flying when I removed it because in was only soldered to one leg. I cannot find where it went! Ugh! It is a 1S953.
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Post by Deleted on Feb 11, 2013 19:50:19 GMT -5
OK, I lost the diode. So I replaced it with an 1N4148 and checked the modulation. It is limited well under 100%, maybe 85-90%. So I jumpered, but no impovement. I then put in a pot temporarily to try that. I was able to adjust to slightly over 100% via scope. I then measured out the pot and it read 14K. I put in a 15K resistors and now she's at 100% and stays there with the circuit intact.
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Post by cbrown on Feb 12, 2013 9:21:32 GMT -5
Still running the Turner with it?
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Post by Deleted on Feb 12, 2013 16:51:37 GMT -5
Yes. That was my original setup in 1983
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Post by cbrown on Feb 13, 2013 9:34:16 GMT -5
Bet it sounds really good right now.  |
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Post by Night Ranger on Feb 13, 2013 15:08:14 GMT -5
Yes. That was my original setup in 1983 The above average selectivity on my TRC-422a has spoiled me. I hooked up one of my other radios and immediately noticed the increased bleedover from skip a few channels away. Night Ranger |
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Post by gator7 on Feb 22, 2013 8:41:23 GMT -5
I had a 1970's TRC 455? AM/SSB mobile that was a great radio. Still have it. Can't remember what is wrong with it. I just remember it was a strong rig. Some day I will get it fixed.  |
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Post by gator7 on Feb 22, 2013 8:48:29 GMT -5
I searched a TRC 455 on ebay. Thats not the correct model. The 455 is a base. Not sure what model. Oh well..
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Post by "Doc"Hammer on Feb 22, 2013 9:04:02 GMT -5
I've got a TRC-455....it's a darn nice old base...mine's pretty cherry..Could it be you had a 451, Gator?....thats a great rig. The 451 had the 8719 PLL and was a stout radio. I have an old fondness for Realistics....for the most part, they were a great line of radios. Quite a few models that stood out as exceptional rigs..TRC-449, 451, 458, 457, 490, 47,30A, 422A, 421A, 455 etc...Along with Cobras, Realistics are probably the most plentiful radio on the planet.
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Post by Night Ranger on Feb 22, 2013 9:15:47 GMT -5
I've got a TRC-455....it's a darn nice old base...mine's pretty cherry..Could it be you had a 451, Gator?....thats a great rig. The 451 had the 8719 PLL and was a stout radio. I have an old fondness for Realistics....for the most part, they were a great line of radios. Quite a few models that stood out as exceptional rigs..TRC-449, 451, 458, 457, 490, 47,30A, 422A, 421A, 455 etc...Along with Cobras, Realistics are probably the most plentiful radio on the planet. The TRC-450, TRC-451, and TRC-453 were all AM/sideband mobiles. The TRC-453 has an LED meter and the TRC-450 and TRC-451 have analog meters. The TRC-450 and TRC-451 look the same on the outside. I think the difference was the PLL chip used. Night Ranger |
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Sandbagger
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Post by Sandbagger on Feb 22, 2013 11:16:08 GMT -5
I've got a TRC-455....it's a darn nice old base...mine's pretty cherry..Could it be you had a 451, Gator?....thats a great rig. The 451 had the 8719 PLL and was a stout radio. I have an old fondness for Realistics....for the most part, they were a great line of radios. Quite a few models that stood out as exceptional rigs..TRC-449, 451, 458, 457, 490, 47,30A, 422A, 421A, 455 etc...Along with Cobras, Realistics are probably the most plentiful radio on the planet. The TRC-450, TRC-451, and TRC-453 were all AM/sideband mobiles. The TRC-453 has an LED meter and the TRC-450 and TRC-451 have analog meters. The TRC-450 and TRC-451 look the same on the outside. I think the difference was the PLL chip used. Night Ranger The TRC-450 used the same chassis as the TRC-490 base (and the Cobra 142), with the single conversion receiver and the MB8719 chip. The TRC-451 was an identical looking radio on the outside, but used the upd2824 chip and had an identical chassis to the Cobra 146. Despite the lack of an easily expandable PLL, the radio was a superb performer, with a super receiver on SSB. The TRC-453 and TRC-465 were virtually identical as well, and was a clone of the Uniden PC-122. |
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Sandbagger
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Post by Sandbagger on Feb 22, 2013 11:19:44 GMT -5
I searched a TRC 455 on ebay. Thats not the correct model. The 455 is a base. Not sure what model. Oh well.. Was it 40 channel or 23? If it was strictly mobile only (no built-in AC supply), and 23 channel, it would be a TRC-47. If it had a built-in AC supply it was either a TRC-46 or TRC 48. If it was 40 channel, it was likely either a TRC-448, or TRC-449. Later models were introduced in the 80's. |
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Post by Deleted on Feb 22, 2013 19:52:44 GMT -5
I searched a TRC 455 on ebay. Thats not the correct model. The 455 is a base. Not sure what model. Oh well.. Was it 40 channel or 23? If it was strictly mobile only (no built-in AC supply), and 23 channel, it would be a TRC-47. If it had a built-in AC supply it was either a TRC-46 or TRC 48. If it was 40 channel, it was likely either a TRC-448, or TRC-449. Later models were introduced in the 80's. I am wondering if he means TRC-457 or 458. |
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Sandbagger
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Post by Sandbagger on Feb 22, 2013 22:33:00 GMT -5
Was it 40 channel or 23? If it was strictly mobile only (no built-in AC supply), and 23 channel, it would be a TRC-47. If it had a built-in AC supply it was either a TRC-46 or TRC 48. If it was 40 channel, it was likely either a TRC-448, or TRC-449. Later models were introduced in the 80's. I am wondering if he means TRC-457 or 458. Those are base rigs. His was a mobile. |
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Post by gator7 on Feb 23, 2013 9:38:22 GMT -5
As I remember mine was a 23 CH w/ extra channels. It had three nimbers for sure, starting with ba 4--. Just can't be sure og thje last 2. I will have to dig it up and find out what the issue is.
73's
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Post by gator7 on Feb 23, 2013 9:42:25 GMT -5
Wow, need to use spell check. So if it has 3 numbers then it ia a 40 channel? That makes it even more of a reason to get it fixed. Thanks everyone.  73 |
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Post by gator7 on Feb 23, 2013 10:19:23 GMT -5
I couldn't take it any more. I dug it out of a box. It is a 448, Needs a good cleaning. and some work. Next I have to find a mic and fire it up to see whats the issue.  |
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Sandbagger
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Post by Sandbagger on Feb 23, 2013 11:03:44 GMT -5
I couldn't take it any more. I dug it out of a box. It is a 448, Needs a good cleaning. and some work. Next I have to find a mic and fire it up to see whats the issue. That was not one of the better RS radios. I had one back around 1981. I got it real cheap because it had no transmit modulation. The problem turned out to be a bad preamp IC, which was not a common part type, and I ended up re-engineering an op-amp to take its place. The radio also had a nasty habit of blowing finals if you happened to change the mode switch from AM to SSB while you were keyed up. Back when I could get 2SC-1307's for $2 a piece it was not a big deal. But they're kind of scarce now. The PLL also had some stability issues too, IIRC. It's probably no coincidence that they replaced the 448 with the TRC-449 less than a year after it came out. The 449 was a FAR better radio. |
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Post by gator7 on Feb 23, 2013 20:31:27 GMT -5
Maybe that's why the guy I got it from wanted to get rid of it. But it did work then. I am going to fire it up in the morning to refresh on the problems. If it turns out to be a major repair, I will 86 it. Hope that is not the case, I really like the 448.
On the other hand, I was looking at a 449 on ebay, and thought maybe i should just think about going that direction, and forget about the 448. Thanks for your input.
73
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Sandbagger
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Post by Sandbagger on Feb 23, 2013 23:06:57 GMT -5
Maybe that's why the guy I got it from wanted to get rid of it. But it did work then. I am going to fire it up in the morning to refresh on the problems. If it turns out to be a major repair, I will 86 it. Hope that is not the case, I really like the 448. On the other hand, I was looking at a 449 on ebay, and thought maybe i should just think about going that direction, and forget about the 448. Thanks for your input. 73 One thing I did like about the 448, was the nice large S-meter..... |
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Post by gator7 on Feb 24, 2013 8:44:29 GMT -5
Yes, that is a very nice thing about the 448.
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