HR2510 Keys up with power.

[Low_Boy]

The TX button works like it should when pushed the TX indication shows. When the microphone is keyed the TX indication shows.

On SSB there is a carrier showing shows power on my meter not on a test radio though. When the microphone is keyed on ssb the power on my meter goes away and when modulated comes back up.

The radio has been totally recapped except the FM board and SWR board. All glue has been removed.
Any Ideas? I remember Andy talking about these radios having self oscillation. Where do I look?

 

[Low_Boy]

Bump Bump..

 

[kopcicle]

Ready when you are

 

[AudioShockwav]

Question.
Does it make any difference if the cover is on or off?

Suggestion number 1.
Look to see if there is a mica insulator under the MRF 477/497 final.
If not unscrew it, carefully clean behind it , add a little fresh heat sink compound, not excessive, you don't need to over do it, add a mica insulator and a plastic insulator for the screw and remount.
I have done this to solve a bunch of weird transmit problems with these radios.

73
Jeff

 

[sp5it]

Insulator under 477 is not needed. Mike

 

[AudioShockwav]

I understand that.
However over the years I have seen this solve some weird TX problems with these radios.
73
Jeff

 

[AudioShockwav]

I have also seen were removing the two pull off disc caps on the bottom of the board at the final solved some weird TX problems.
The 2510 I am running in my pickup right now has the 2 caps removed, the insulator installed and a 497 final.
Works very well for a 30+ year old radio.
73
Jeff

 

[sp5it]

Was it behaving like that before recapping?
What about removing silver board? Do you see power on "meter" (What meter? on radio LCD or external wattmeter)
Mike

 

[Handy Andy]

Wish I could give you EASY answers...

However they're not...

The ones I've dealt with are "Show me" types - the techs at the old office had some come thru that needed newer finals...nearly every one - when the "Glue" gets removed, needed new Bi-filar winds. That means you take the Toroids out and redo the windings with fresh wire - not hard but you need to replace the old ENAMLED wire with new. As these "Heat up" from use, one or two winds actually will "short" due to the Enamel gets baked off one wire so the other carbons up and eventually they both fail - generating a "key up" or self-oscillation problem they say related back to the types of Toroid winds and their lack of protection from bouncing and otherwise being used - just plain rubbed or "welded together" - it is a usage in mobiles problem at times because one wire got too hot and burned off it's enamel it ground against another - jostling as you'd have in mobile setups did not help either...

They told me that Uniden was well aware of the problem and that unless you use a different design of transistor for the MRF477 - you can't avoid this circulation current problem.

• They're nice when they work right, but if anyone nicked a wire in assembly or outside in the field in these toroid's - look out!
• When you Re-cap - be sure to use the Highest Grade possible to reduce the inductive effects the cases exhibit on their values. Basically they're saying to use Computer Grade types and if possible avoid Standard Aluminum Electrolytic types, use non-acid Niobium types. Yes their SMD but you can fit them in there...they say...

Now they (O-techs) did say that the "Rear Panel" problem was also another type of inductance reactance problem that dealt with how the rear panel will ground to the rest of the radio - that heat sink panel was aluminum and the case was steel - you have dis-similar metals problem - you can try to tighten screws and see if the problem clears up but more than likely the "spacer" was needed because of the MRF 477 and it's Emitter having a good if not better path to ground - making the rear panel more of a giant ground plane that would add to the ground looping problem. Those 561 twin caps were needed to offset this...

Strong signals present in the Antenna were also found to have caused self-oscillation when the radio is sitting idle waiting for a call - you'll hear bleed over then silence - like a squelch activated thunk along with a swoosh - by feeling the rear panel you discover you have a hot radio. These issues, when they cropped up - are from those toroid's being so broad banded. Can't avoid the back feed feedback issue unless you redo the entire strip as well as do up better wind designs to neutralize the incoming signals from causing a regenerative feedback loop.

 

[Handy Andy]

To help you better understand the problem as I see it...

Your TX issue may not necessarily be with the "Glue" nor with the Biasing or inductive problems...

Well, maybe inductive...

Hear me out...

​

• The above represents and is from Wikipedia about Electrolytic Capacitors and their construction.
• IT appears as an Inductive as well as Capacitive circuit with resistive elements as both in series with (thru the dielectric) as well as parallel - again with, but across the dielectric...
• IF you have never had one blow up inside a radio - you'll be hard pressed to imagine the amount of tiny foil bits these parts can hold.
• They are wound with a spacer in-between two plates that are insulated and yet anodized to from a dielectrical surface to work as a means to hold and transfer charge - diametrically opposed charges.
• Because of this wind construction - they look like large inductors in high-frequency applications - which offer a source of power for circulating currents within the part - generating heat and emit a gas when this occurs.

All you may need to do is just swap several of the power feed caps used in the radio with better and perhaps even smaller values so they themselves don't hinder the effects of this high-frequency regenerative effect of looping currents circulating between the back panel and the ground plane of the board. The higher the Farad - the greater surface area for this inductive problem to occur. So use as small as you can get away with to clean that up.

 

[Low_Boy]

It was doing this before recapping. Showing key up on internal meter and external bird meter. No power with silver board removed. When keying up on power it is off freq. But when mic is keyed it shows correct freq on external meter. Not a mic problem. It will cry with out mic plugged in. Covers off or on and fi

 

[Low_Boy]

Q125 was bad. It is kind of coming back from the CB Tricks days.

 

[kopcicle]

woo hoo!

 

[undertaker]

send it to Rogerbird….

 

[Handy Andy]

Whew...else you should read that Wiki article - anyone whom does will see a nice write up on the "Time line" Lifetime event stuff. Makes this 10V cap blues - pretty spot on in regards to the Mean Time Between Failures (MTBF)

Glad to know Q125 was the issue - nothing more....

2SB525 - 8V TX Switch...hmmm...