View Full Version : Amp locks up

05-20-2014, 06:19 AM
I recently bought a texas star 350 and a ranger 6900f25. The amp works well with my old uniden but if it's on hi and I key up with the ranger it locks up. (stays engaged after I let off the key) Only happens on high if on low or ssb it doesn't do it. Anyone have any ideas what could be causing this?

On another note both D-104 mics squeal when used with the amp no matter which radio I am on. Any ideas what I can do to stop this?

Thanks in advance for any help.

05-20-2014, 07:05 AM
On high you have over drive. Check out the grounding solutions the ham banders use. Requires grounding your radio, amp and microphone together. If it is a base station to the earth as well.
Do they squeal with out the amp? I have seen microphones miswired that squeal like pigs.

05-20-2014, 11:44 AM
Another source of the interference could be a loose cabinet element(vibration) or even a loose transformer core. That's assuming proper grounding to start.

05-20-2014, 11:46 AM
"On high you have over drive. " Can this be fixed anyway? It does it even with the radio RF power all the way down.

No they only squeal with the amp on. When I get time I will try grounding everything. I have a ground rod I just need to drive it in.
Funny the hand power mic I have doesn't squeal.

Thanks Tallman

05-20-2014, 07:37 PM
The D-104 was prone to getting over driven, it might be the element (head) just doesn't like all that extra RF.

05-20-2014, 10:21 PM
It does it even with the radio RF power all the way down.
No they only squeal with the amp on.
Thanks Tallman
Try putting some distance between the amp and the radio. I had a KL-500 that would "Latch UP" because it was too close to the radio. It would cause the amp to oscillate even when unkeyed. Another thing you can try is to put one of those clip on ferrite chokes on the microphone cord down on the radio end of the cable. On my D-104 I put a heavy gauge wire up through the coils of the microphone cord and grounded it to the station ground. Also check for leaky coax. If your cables have grounds that loose the cable will radiate and cause problems.

05-21-2014, 06:24 AM
I've got about 4 feet between them now. I will try grounding everything together and to earth this weekend if I can find time. All my coax is heavy duty and in good shape best I can tell the main line is new LMR-400. I do want to get some LMR-400 jumpers to match the rest. If I can find some ends to fit I have quite a bit of excess coax on the main line I could cut into jumpers. How do I check for leaky coax? All the connectors are tight.

The cords on the D-104's are both small old and kinda crappy looking I was wondering about replacing them.

Thanks for the pointers. :)

05-21-2014, 09:17 AM
Grounds, don't you just love them?? The troubles caused and remedies, I could write a book. Electrical grounds that come into the home via pole mounted wires and a ground that you drive yourself can have a potential difference that can be a serious hazard. The first step is to prepare your location for a ground stake. I use an 8 foot copper clad, iron stake, driven into the bottom of a three foot post hole. Leave 8 to 10 inches above grade. You could line that hole with coffee cans with holes top and bottom. A mixture of sand and rock salt could be used in parched areas in the top of the hole. Wetting the salt/sand would enhance conductivity. Flat nickel plated copper braid should be used on this length to the first grounding point. Lengths of ground wire can be tuned, just like coax to help with SWR and TVI.

05-23-2014, 12:19 PM
is the amp new ? it could be a bad keying relay thingy . contact mike at ......


btw ..... how high is the deadkey on that 6900 ? could be too much for the relay ... ???

05-24-2014, 12:58 PM
Dead key radio turned down to low is about 2w swinging better than 20w. The amp works good with my other single final radios. Also works okay with the 6900 long as the amp is on low, but won't work without locking up on high. I think the combination is just to much. IDK