RT-524 Failure

[JDToumanian]

Well I was excited to use my RT-524 for the first time on the way to Camp Dirtbag, but it's transmitting circuits failed within 5 minutes.

I know I had everything hooked up right, I've triple checked it, I have an MX-7777 suppressor and a VIC-1 intercom and everything was working perfectly. The VIC-1 is still working and the radio is still receiving. I had tested the RT-524 using a scanner and it was transmitting great. Here's the rundown...

--RT-524 no longer transmits at all. VIC-1 and all receive and squelch functions are still working. The display light is still working and the speaker, volume, etc. work.

--The blower motor no longer comes on when pressing the PTT switch.

--The antenna no longer auto-tunes when changing channels.

--It is not the X-mode setting or the 'terminator' cap.

--I swapped around all cables with spares that were also known good. No difference, so I believe all cables are good.

--I tried plugging the headset/mic into the radio directly... No change.


I believe something in the radio failed. I looked inside to see if there was anything obvious, like a connector unplugged or something, but everything looks normal. It failed without any notice.... We were not driving or doing anything to the radio at the time. One minute I was talking to the deuce next to me and then he suddenly could no longer hear me.

Anyway, I would like to get this repaired by Tower Park next week. I've been reading the manual but there really does not seem to be much that I can do without the military radio testing set, as all the troubleshooting charts seem to be telling you to hook it up to that set. So it seems my only chance to get it going is either someone here will have an idea which module it likely is (common failure mode?) or someone here in So Cal has a test set (NF6X?) and can help. I will pay, I don't expect to use someone's time, knowledge and/or equipment for free.... Unless you get a kick out of repairing radios or something.

If I can't get it done by Tower Park I'll end up buying a test set and doing the diagnosis and repair myself, I really don't want to ship this thing out to someone. I'm no electronics whiz, but I'm not incapable either.

Thanks for any advice you can give...

Regards,
Jon

 

[tennmogger]

Was the antenna matched for the frequency in use? High SWR could cause heavy current in PA (power amp) and maybe blow a fuse? Maybe HV failure?

Just guesses.

Bob

WB4ETT

Well I was excited to use my RT-524 for the first time on the way to Camp Dirtbag, but it's transmitting circuits failed within 5 minutes.
..chop...

 

[Blood_of_Tyrants]

I have worked on old military radios and it sounds like the transmit relay has gone bad. In older radios, when you press the transmit button, you are energizing relays that switch the radio from receive mode to transmit mode. It seems to me that either the wiring or the transmit relay has failed. If you could send me a schematic, I could probably let you know which relay.

 

[JDToumanian]

It's FIXED!

I e-mailed Steve Haney and described the problem just as I did in my first post here, and he responded that I should take the covers off and look at the high voltage circuit breaker..... Sure enough, it was tripped and was not self-resetting when the power was turned on. I called him to thank him for the quick diagnosis and to find out how much the breaker would be, and he said that they rarely need to be replaced, you just need to get it to stay reset.... I flipped it back and forth a few times, and it stayed! He said this sometimes happens and whatever freak occurrence that caused it to trip rarely repeats itself... If it does, then either the breaker is bad or it indicates trouble elsewhere.

Anyway, Steve is the best in my book.

Jon

 

[Billy Bobbed]

Thanks for the info.JD.I have my radio RT-524 ordered from pvjarhead still waiting.Nice to know if it happens to me.

 

[Rustygears]

Make sure the radio has a good match when transmitting. Just because it has an autotuner doesn't mean it has achieved a safe match. The breaker is there to protect the power supplies and finals. A mismatch will cause excessive current and fry either or both. Get hold of someone who has an SWR meter and make the quick and simple check.

 

[tennmogger]

Right on the money, Rustygears.

A common misconception is that the "tuners" in some antenna bases actually care what the SWR (reflected power) is. They don't. These antenna 'tuners' simply step to a combination of inductance and capacitance preset to positions guessed at by the manufacturer, for some range of frequencies. Any variation in frequency within the band, or changing antenna characteristics, even the individual truck installation, can cause the true reflected power to be way off.

Older sets, especially tube-type stuff, have no protection against being mis-matched. The PA just draws more current. Maybe it survives, maybe not.

I don't know what type antenna is in use, but it's always best to pick your expected operating frequency (like 51 MHz) and tune the appropriate antenna base switch position to match that frequency. With antennas like the AS-1729 with the switch in the base, a mismatch is practically guaranteed every time. A simple whip, like an AB-15 base and appropriate MS-116 series elements, actually cut to match, will outperform the AS-1729 any time, IMHO.


Bob WB4ETT

Make sure the radio has a good match when transmitting. Just because it has an autotuner doesn't mean it has achieved a safe match. The breaker is there to protect the power supplies and finals. A mismatch will cause excessive current and fry either or both. Get hold of someone who has an SWR meter and make the quick and simple check.

 

[breaktime]

I realize this is a very old thread but thought I'd be best to ask here first-

Same problem. No transmit... Can anyone describe where inside the RT-524 / RT 246 case the 'high voltage circuit breaker' (mentioned above) is located?

Image - screen capture from that old training film

Thanks ,
Jim

 

[SCSG-G4]

Download and search the TM 11-5820-401 manuals (the -10, -20, -34 -34P, etc.) and see if you can find it.

 

[Flyingvan911]

Steve Haney is a great guy. He got my RT-524 going after I got it off EBay. He is highly recommended.

 

[papakb]

Both circuit breakers are mounted on the inside of the front panel. When you turn the radio on you aren't actually moving the circuit breakers, your just telling a relay that you want to power up the radio. If one of them trips then it is reset by cycling the Off - LOW - HIGH knob on the front panel. The breakers are small gray boxes and the bracket that adjusts them can get bent out of position by rough cycling the switch. It can be bent back into position if you know where to look but it isn't an easy job and the front panel has to be removed from the radio to do it.

Removing the front panel is a pure PITA. First you need to set the radio to 30.00 Mhz. Then you need to remove the front panel screws along with the connectors to the receiver and CRS trays. The antenna relay needs to be disconnected along with the grounding straps from the tuner to the radio chassis. There are coax cables and power leads that need disconnecting. Not a simple task. When reinstalling you need to make sure the oldham couplings between the tuner module and the PA section are in alignment or mechanical things get bent. This job is better left to someone that knows what they're doing or you might end up with a 62 pound wheel chock.

 

[breaktime]

Both circuit breakers are mounted on the inside of the front panel. When you turn the radio on you aren't actually moving the circuit breakers, your just telling a relay that you want to power up the radio...
<cut>

This was a really great post. Thank you for taking the time to write that.

Download and search the TM 11-5820-401 manuals (the -10, -20, -34 -34P, etc.) and see if you can find it.

I have had the TMs in .pfd for many years. I tried and gave up. I have many reasons why they are plan B, probably the #1 reason is that I am lazy (and looking for a really great post).

Steve Haney is a great guy. He got my RT-524 going after I got it off EBay. He is highly recommended.

I got two R-442 knobs (w/ screws) from Steve. It was a special request via an ebay message. I appreciate that very much. Those knobs have been on my to-do list for years. Now I have a little less to worry about ( stress). I still have a massive list but with help from Steve (and SS members) it, and my stress, are moving in the right direction.
Jim