Radio Shack HTX-252 VHF no transmit

[Murphy625]

I bought a Radio Shack HTX-252 as part of a package deal at an estate sale.. Its a 25 watt vhf radio.

Seems to be in good cosmetic condition but it doesn't transmit.

When you push the PTT, the power meter says its transmitting, but no signal comes out.. Nothing is picked up on any other 2 meter radio in the room and my VHF SWR meter shows no deflection.

I take it this means it has blown finals?

Is stuff like this worth fixing? I opened it up to check for "the obvious", but no luck.

 

[K4EET]

<snip> When you push the PTT, the power meter says its transmitting, but no signal comes out.. Nothing is picked up on any other 2 meter radio in the room and my VHF SWR meter shows no deflection. <snip>

Do you have access to a frequency counter? I'll get to that in a second. Not sure what you mean by "my VHF SWR meter shows no deflection". What radio are you referring to? The Radio Shack HTX-252 or the receiving radio? If on the HTX-252, are you saying the power meter deflects but the SWR meter position does not move? That would be "normal" if you are transmitting into a perfect load. As for a frequency counter, that and an external power meter into a dummy load would tell you for sure whether the rig is transmitting or not. It may actually be transmitting on some frequency that you don't expect it to be transmitting. Be careful about that!

Here is the Service Manual for the HTX-252:

http://www.repeater-builder.com/radio-shack/htx-252/htx-252-svc-man.pdf

The Radio Shack HTX-252 is actually an Albrecht AE-540. Are you able to use the Service Manual to troubleshoot the rig?

Let us know the answers to these questions and we may be able to help you further.

73, Dave K4EET

 

[k6cpo]

So many people completely miss the concept of front end overload when testing new radios.

If you transmit on a radio, especially at higher power outputs, another radio in close proximity on the same frequency will go deaf. The power of the transmitting radio will overload the receiving radio and it will go silent.

This happened to me just last weekend. I stopped by where one of our local clubs was set up for the annual lighthouse weekend. I was sitting in a chair holding my HT when an operator less than ten feet away transmitted on 146.520. Each time he keyed his radio, I heard the first two or three words of his transmission, then my radio went dead.

The best way to test a radio is to call out on either a simplex frequency, or on a repeater and see if you get a reply.

 

[K4EET]

^^^ What K6CPO said but I do hope they are using a dummy load. I don't believe he has a ham license yet. 73, Dave K4EET

 

[Murphy625]

Do you have access to a frequency counter? I'll get to that in a second. Not sure what you mean by "my VHF SWR meter shows no deflection". What radio are you referring to? The Radio Shack HTX-252 or the receiving radio? If on the HTX-252, are you saying the power meter deflects but the SWR meter position does not move? That would be "normal" if you are transmitting into a perfect load. As for a frequency counter, that and an external power meter into a dummy load would tell you for sure whether the rig is transmitting or not. It may actually be transmitting on some frequency that you don't expect it to be transmitting. Be careful about that!

Here is the Service Manual for the HTX-252:

http://www.repeater-builder.com/radio-shack/htx-252/htx-252-svc-man.pdf

The Radio Shack HTX-252 is actually an Albrecht AE-540. Are you able to use the Service Manual to troubleshoot the rig?

Let us know the answers to these questions and we may be able to help you further.

73, Dave K4EET

Thank you for the service manual! That should help tremendously..

I do not own a frequency counter but I do have an oscilloscope and various other tools I might be able to make work for some basic troubleshooting.

I'm in a very rural area and any transmitting I do in my basement for testing isn't going to go further than a few feet.. I doubt it would even make it through my roof since everything is covered with radiant barrier foil insulation.. (which acts like a giant Faraday cage).

My SWR meter also reads power and its not showing anything coming out.. Even on SWR mode, there should be some movement of the needle yes? I have a N9TAX antenna and it moves the needle ever so slightly on a 5w HT (FT60R).

I'll have to wait for a rainy day and then dig into this radio to see if I can fix it myself. I have enough electronics training to know that I don't know anything about radios, so it might end up as a paper weight.


I'm wondering how long it would take one of these ham radio repair places to diagnose and fix it... IE: how much it would cost. Its probably a 50 cent part but how long it takes these guys to find it and replace it is another story.

 

[N4KVE]

I'm in a very rural area and any transmitting I do in my basement for testing isn't going to go further than a few feet..

That's like not having a driver's permit, and driving it in your driveway, & saying "it's OK, I'm only driving it a few feet". It's still illegal. I just don't understand why people buy a transceiver before they are legally allowed to transmit. You want to listen, OK, just don't plug in the microphone until you are allowed to transmit.

 

[K4EET]

Thank you for the service manual! That should help tremendously.. <snip>

You are certainly welcome. The one thing that you should purchase, if you don't already have one, is a Dummy Load. Look into getting a Dummy Load rated at at least 30 watts at 150 MHz to handle the Radio Shack HTX-252 which has a 25 watt output.

You could also look ahead to when you are licensed and might get an HF rig that puts out say 100 watts. If you get a higher power Dummy Load to handle the HF radio's 100 watt output, you'll only have to buy the Dummy Load one time. Of course, if you were to get a linear amplifier, you'll need a Dummy Load that can handle up to the legal limit for amplifiers.

As N4KVE stated, you are illegal if not transmitting into a Dummy Load. Here is a 300 watt Dummy Load good for up to 650 MHz that only costs $39.95 which would be a good investment:

https://www.dxengineering.com/parts/mfj-260c

So please, do seriously consider investing in a Dummy Load. Then, based on your skill set and test equipment that you have, you just might find what the problem is. And don't forget about what K6CPO said, watch out for overloading the front end of the receiving radio. A Dummy Load would also help to avoid that problem.

Best wishes on getting your two meter working. Keep us informed on your progress. I, for one, will be interested in following your progress.

73, Dave K4EET

 

[Murphy625]

Oh wonderful.. I probably have 10,000 resistors in various mayonnaise jars.. all neatly categorized and labeled.. and not a single way to make a 50 watt load.

And all the big hotdog sized ones in shoe boxes are all wire wound that come from servo controllers.

A little luck would be nice.

 

[K4EET]

Oh wonderful.. I probably have 10,000 resistors in various mayonnaise jars.. all neatly categorized and labeled.. and not a single way to make a 50 watt load.

And all the big hotdog sized ones in shoe boxes are all wire wound that come from servo controllers.

A little luck would be nice.

LOL! Awww come on... Go ahead and splurge on the $40 Dummy Load... 73, Dave K4EET

 

[Murphy625]

LOL! Awww come on... Go ahead and splurge on the $40 Dummy Load... 73, Dave K4EET

I like building stuff.... and I order from Digikey all the time so I'll just get some resistors on my next order.