Needing Info On Palomar 250tx

[sanjosebay21]

Hello guys i have a freind who has this amp and he llikes to talk to ssb hes been doing it for a while now and wants to do it with this amp but when he keys up the relay only keys for a split second and then unkeys until he talks is there any ways to get this to key up right on ssb? and he knows it not legal and all that stuff just would like info on how to do this just something he wants to try. any help much appreciated ................73's

 

[9C1Driver]

Is it one of the old school real Palomars that says TX250? That amp should have auto SSB. This means all he has to do his key the mic and talk. Since SSB has no carrier if all you do is key the mic but don't speak the relay will unkey after a split second. So what you described is normal, should be ready to go.

 

[psycho]

Is it one of the old school real Palomars that says TX250? That amp should have auto SSB. This means all he has to do his key the mic and talk. Since SSB has no carrier if all you do is key the mic but don't speak the relay will unkey after a split second. So what you described is normal, should be ready to go.

You have it backwards, the old school Palomars have switchable ssb delays.

 

[sanjosebay21]

Here is a pic not sure how old but it looks old......

 

[Robb]

Might have a problem with the relay.

 

[sanjosebay21]

it works fine on am just wont go on ssb puts out a whopping 160 watts avg....about 175pep i would think if there was a relay problem it wouldnt key at all i wouldnt think there is a ssb part for the relay right ?

 

[TonyV225]

Im sure its A/B biased and that would be auto SSB so no AM/SSB switch is needed. As mentioned above there is no carrier as AM/FM have so when you key that amp on SSB like all amplifiers if your not talking it will automatically switch the relay off until audio is applied.

If he is getting forward power when he speaks into the microphone when on SSB then all is working as it should. Thats a small amplifier but yet perfect as far as output power. Without knowing what final transistors are in the amplifier I cant really say what it should be doing as far as power.

 

[sanjosebay21]

it has 2 2sc2879's in it and you can key up and talk yes swings up but you gotta be fast the second you go to say another word it unkeys then keys back up so you gotta tlak real fast

 

[Robb]

You might check the electrolytic cap that is on the board that keeps the relay closed in SSB mode. It may need to be changed to a higher value to keep the relay closed; that may take some experimentation. But it may have just failed too; check and see if the top of that cap has expanded. If it has, just replace it with a new one that has the same capacitance (in 'uf') and voltage. Make sure that it is polarized correctly, as electrolytic caps are polarized "+" and "-".

As far as power output goes, that may be the result of the meter being inaccurate. Or, you don't have a big enough power supply running the amp. It needs a ~40 amp supply to run a pair of 2879 output transistors. Not enough amperage from the power supply; then not enough output from the amp. Should put out about ~275 watts with 20 watts into the amp @ ~13v. No more than 20 peak watts into the amp from the radio - if you want to keep this amp alive. You also need 8 gauge multi-strand wire to get all of the amperage to the amp from the power supply as well.

Food for thought . . .

 

[TonyV225]

The Capacitor might even be bad so when looking at that particular Cap look to see if its bulging out. For example, look at the top and bottom and check if they are bulged and split or cracked open fluid also leaks out in most cases and will leave a brownish residue on the board under or around the Capacitor itself.

Also that amplifier should do between 250 and 350 watts on SSB with 2 x 2SC2879 transistors in it. I know 100 watts a big margain but there are a few factors that come into play like voltage being run into amplifier ETC.

 

[9C1Driver]

it has 2 2sc2879's in it and you can key up and talk yes swings up but you gotta be fast the second you go to say another word it unkeys then keys back up so you gotta tlak real fast

From the picture I see it's not one of the old school Palomars. It should however have auto SSB as stated. At this point I think someone made the mistake of trying to "upgrade" the finals. A Palomar 250 should not have 2879's. Hard to say what else they did or did not do so it probably has an issue.

 

[TonyV225]

Yes that amplifier should have 2 X SD1446, 2SC2290, SRF 3749 OR MRF-455 99% of the amplifiers that have a pair of 2SC2879 are listed as 300 - 350's

 

[sanjosebay21]

Yes originally had 2sc2290 in it but it has been reworked a few caps and resisters changed and some rewraping hes only running a 10amp power supply ill hook it to a battery later and see what it does power wise maybe maybe 10amps not enough to key on side band if it requires certain amount on am for full power possibly needs more amperage for ssb? thanks everybody for your imput and information.

 

[9C1Driver]

In stock trim that amp would have a 20 amp fuse either inside or in the power cord. You could expect a 14-18 amp draw depending on what mode, peak input, and what voltage level. All bets are off now that it's been janked up, a Texas Star 350 with 2879 finals runs on a 30 amp fuse.

If all you have is a 10 amp power supply you should stop right there. You can damage the amp, power supply, or both. Try it on say a 35 amp power supply and see what happens, then go from there. It can be tough trouble shooting an amp after it has been improperly modified.