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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1282
Registered: 9-2004
| | Posted on Saturday, March 11, 2006 - 9:59 pm: | 
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hi all,
a friend asked me to look at his HR2510 because it was dimming the lights on the radio upon keyup, and the volume control was scratchy.
both problems fixed within a few minutes.
he had the thng running to a cig. lighter plug. (then into his power supply!)
new connector and wires. done.
a little contact cleaner, done.
OK, he bought it used and hasnt put his hands in it.
he doesnt have the multi pin cord, so there is a jumper on two of the pins on the back of the radio.
inside the radio, the wires coming off of the multi pin connector are going to two relays that are glued to the board, (doesnt quite look factory) they each seem to be switching in a resistor .
i noticed that the receive audio was a little scratchy, and upon poking at one of the relays, the receive cut in and out.
what are these for, and can i just jumper past them?
he's not going to buy the cord to use them for whatever they are for.
second issue, the AM power is low. it will only go from about 1/2 a watt to about 3.5 watts. swing to maybe 5.
SSB power can be turned as high as 32 watts.
anyone know of any common problems in this chassis?
can anyone hazard a guess on the low power?
am i not seeing a hi lo power switch on the front?
the last thing i noticed was that the ground lug on the SO-239 on the back of the radio is not soldered to the PC board.
it looks like it was.
should it be?
my mind says that it should, but i want to check with someone who's more familiar with this cahssis, or owns one that they can check this on.
thanks for any help and also any tips or tricks on this chassis that anyone can offer,
matt |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1132
Registered: 6-2004
| | Posted on Saturday, March 11, 2006 - 11:25 pm: |
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I'm guessing at least one relay is some form of talkback removal.
A common modification for this chassis is to use the SWR calibrate pot for AM carrier power control. It's possible that the pot was either replaced or damaged if this modification was done improperly and then reversed. Other than that I don't know what might have been done. Maybe an attempt at swing modification?
Yes, the ground lug on the SO-239 should be soldered to the board - at least it is on mine.
This very well may be the most modified CB/10 Meter radio ever. There were books, clubs, and newsletters about this radio long before most people were ever aware of the internet. Good luck in finding and reversing any modifications currently made to your friend's radio. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1285
Registered: 9-2004
| | Posted on Sunday, March 12, 2006 - 1:40 am: |
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thanks so much for the input hollowpoint!
thats exactly what i needed to know. (especially about the ground lug)
i checked out rogerbird's site, and i found that the pot marked AM POWER in the radio is VR103.
im reading that the real AM power pot is VR107. that would explain why i couldnt adjust it.
i'll try it when i get home. (this is my late night at work)
the SWR cal knob was not converted thank heavens!
i will check out the talkback removal. it seems like a good bet as this radio has no talkback at the moment.
have you tried the transistor change for improved receive? its on regerbirds site.
thanks again hollowpoint; you've helped a lot,
matt |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1286
Registered: 9-2004
| | Posted on Sunday, March 12, 2006 - 1:54 am: |
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hollowpoint, i just checked out the talkback fix you mentioned.
im pretty darn sure thats exactly what ive got here.
there's no rectifier diode on the relay in the radio ive got, so im guessing that the contacts have arced over the years and that's what's causing the intermittant RX cutout.
im just going to remove it and use the diode method to get rid of the talkback.
once again, thanks for your invaluable input.
matt |
Semi
Junior Member
Username: Semi
Post Number: 17
Registered: 7-2005
| | Posted on Sunday, March 12, 2006 - 5:01 pm: |
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Hey kid.
If turning the correct pot doesn't get you any more carrier on am I would check Q122 or 113. Change them both 945's they are near each other looking from front and top,they are on the left side to the right of the 8v reg. that's mounted on the chasis.
Let me know how you make out.
Semi |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1289
Registered: 9-2004
| | Posted on Sunday, March 12, 2006 - 10:15 pm: |
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thanks semi, and to hollowpoint,
the cure for the low power was to turn the correct pot.
dead key goes anywhere from .5 to more than 25 watts.
i noticed that after about 7 watts, that the modulation goes downward.
is this normal for this radio?
the radio seems to modulate fully, but only swings forward about a watt and a half.
i know this chassis is low level modulated, so maybe this is just the way it is.
is there any way to increase the forward swing a bit without removing any modulation limiters?
the VR for AMC is all the way up.
the relays were exactly as you said hollowpoint.
i took the one for the talkback out and did the 1N914 diode from pin 6 of IC103 to middle pin of Q125 (not sure of the number right now, but i did it on the correct transistor)
talkback is gone, but after unkeying, the radio stays keyed for about another second or two.
is this caused by the diode i added?
not a big deal, but i would like to fix it if i can.
soldered the ground lug, SO-239 was loose, which had caused it to break free.
all in all, im happy, but would like to see some more forward swing, and fix the RX/TX lag time issue.
thanks for all the past and future help,
matt |
Semi
Junior Member
Username: Semi
Post Number: 18
Registered: 7-2005
| | Posted on Monday, March 13, 2006 - 8:27 am: |
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Kid
Try spreading the coil on the back row farthest left, don't have a radio in front of me now so I don't recall the #L but that generally helps. The other small coils on the output chain may have some effect also.
Radio has the capability to swing RMS to 15 - 20.
from 2-3 watt dk.
Semi |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1134
Registered: 6-2004
| | Posted on Monday, March 13, 2006 - 9:05 am: |
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7 watts is about it for AM with 100% modulation. I believe it came from the factory adjusted to 10 watts, but it really can't swing to 100% modulation without some changes, and for an additional few watts it's not worth it in my opinion.
I've said this before and I'll say it again, you will not see much AM forward swing on any radio with a properly adjusted AMC circuit. I don't trust modulation meters or PEP meters that don't have an amplification circuit, and even then I think they are virtually worthless compared to either a modulation scope or an oscilloscope. Use a decent RMS meter instead. Throw a constant tone into the microphone and at the most you'll see 50% more average power, and because of the human voice's dynamic range it'll never reach that potential with voice alone. It's more like 10%-30% average modulation depending on the compression levels used in the audio circuit. That amounts to 15% maximum forward swing on AM with voice alone. That's not much swing. If you see more with another radio it's either harmonics, over modulation, or noise in addition to voice. The only way to get real modulation levels approaching 100% is to use some form of AF or RF clipping processing, and no CB or "10 meter" radio has that type of processing.
I don't know if the diode creates a delay in the radio. Neither of my 2510s had talk back and don't exhibit that characteristic. There is a very small circuit board with some SMD components installed on the foil side of the main board in the area where the diode modification is supposed to be done, so maybe mine came from the factory that way. It looks awfully well done to have been a modification done by a distributor. I've never investigated what the circuit actually does.
To see if the diode is responsible you could unsolder one end of it and try the radio. If the delay goes away and comes back when you solder it back you can safely say that it's causing the delay. Why? I wouldn't know. Double check to see if it's soldered to the correct points and if it is, maybe you can try the other diode fix instead. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1135
Registered: 6-2004
| | Posted on Monday, March 13, 2006 - 9:24 am: |
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Don't EVER spread coils. They're there for harmonic supression. If you get more power output after spreading the coils you are just seeing harmonics. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1293
Registered: 9-2004
| | Posted on Monday, March 13, 2006 - 11:29 pm: |
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thanks again guys,
the meter i am using is an RMS meter, even so, i dont trust the numbers; just the differences in the readings i see when changes are made.
i also disagree with spreading the coils. it might show a few watts, but where are they going?
i will try to remove the diode. i have to admit that i installed it before i checked to see if the radio had talkback.
mine has that small board in it too.
thanks again,
matt |
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