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Legend
Junior Member
Username: Legend
Post Number: 32
Registered: 12-2002
| | Posted on Tuesday, April 13, 2004 - 10:51 am: | 
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Hi...
I just recently acquired a Palomar Skipper. There are two things I would like to fix, if you can help me out here.
1) I believe the transformer is about to give up the ghost. It makes a buzzing noise that is getting progressively worse, and seems to be especially bad when the amp is at full operating temperature. Do you know where I can get a transformer that I can use as a replacement for this amp? Anyone know the make, and numbers on this transformer?
2) My transmit works fine, and produces about 290 watts deadkey with 2.5 watts in. It swings to about 450-470 P.E.P. on sideband (is this about right for 8950's?). However, I believe my sideband relay is messed up. Sometimes when it is in SSB mode, the power will suddenly drop down to barefoot output. Then, when I unkey it, and then keyback up, it is putting out full power again. Sometimes I have to key up several times to get the output back.
If I key up with the radio on AM, it will do the same exact same thing (Power drops out) IF, and only IF, the SSB mode switch on the amp is still set to SSB.
Do you think the SSB relay is bad? If so, would the power drop out like that? I am almost certain that it is a relay problem. Also, if so, which of the three relays in the back of the amp (mounted on a PC board) is the right one?
Thanks for your time and consideration. |
Legend
Junior Member
Username: Legend
Post Number: 34
Registered: 12-2002
| | Posted on Wednesday, April 14, 2004 - 1:57 am: |
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Yo... There's got to be at least a dozen Skipper experts on this board.
Yoohoooo....
What-d-ya-say? |
Buck
Advanced Member
Username: Buck
Post Number: 864
Registered: 3-2002
| | Posted on Wednesday, April 14, 2004 - 6:39 am: |
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Mine cuts out also sometimes....I traced it down to the relay like you did....If you find a fix let me know. I hardly ever use mine though. Mine hasnt been on in about 3 months
Buck |
Legend
Junior Member
Username: Legend
Post Number: 35
Registered: 12-2002
| | Posted on Wednesday, April 14, 2004 - 9:42 pm: |
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So... do you know which relay is causing the power to drop out intermittently, and if so, where it is located?
Mine did it last night, even with the SSB/AM mode swith set to AM, for the first time. I'm sure it's a relay, but I don't know if it's a keying relay, or what. Maybe a tech could help us out... Eh?
Yooohooo... anybody home? |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 739
Registered: 3-2003
| | Posted on Wednesday, April 14, 2004 - 11:34 pm: |
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Legend
The A/M-SSB switch has nothing to do with it sticking. If you will notice, when it is in the SSB position, the relay will be delayed a bit during its "unkey" cycle. There is a capacitor in circuit that has to unload when there is no longer any RF power present. Basically, all this capacitor does is slow the relays down and keep them from chattering while in the SSB mode.
I don't recall how many tubes are in this model but if there are only two 8950s, then yes, 450-470 PEP on sideband is out of the question. Like I said, I don't remember the number of tubes in that particular model. But whatever you do, DO NOT OVER DRIVE THEM. They are quite rare these days and if you just happen to find any more of them, you'll be paying through the nose for them plus your first newborn son.
Personally, I would tread lightly on that linear and back your input power down. It doesn't have to be hammered hard. If it indeed does 450-470 watts output, no one would ever know if you backed the power down to 300 watts. It would run cooler and the tubes will live longer with less SSB input power.
As far as the relays go, first unplug the amplifier and DISCHARGE THE CAPACITORS AT THE POWER TUBES. Then get in there and clean the relays. It's just possible that all the relays need is a good cleaning. Run some clean white paper through them and see if you find any dark residue on the paper.
After that, spray them with some good contact cleaner. Another reason why relays can stick is from over heating due to over driving and/or incorrect tuning.
Next, check the little nuts and bolts that are used to mount the transformer to the chassis. They may be a bit loose. If it stops buzzing when you push down or put some weight on the transformer, that tells me that it has definately loosened up a bit. Another thing you can try is to put a rubber foot on the bottom of the chassis directly under the transformer so it can be better supported. I've had to do this with a couple of heavy-duty power supplys--works great.
If someone on the air is hearing this "buzz" or "hum" when you key with zero audio, then replace the big filter capacitors. Old and leaky filter capacitors will no longer filter out a 60 cycle AC hum.
I hope this may help you. I'm sure there will be other ideas posted here as well.
Jeff, kc0gxz. |
Tech808
Moderator
Username: Tech808
Post Number: 2144
Registered: 8-2002
| | Posted on Wednesday, April 14, 2004 - 11:50 pm: |
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Jeff,
Belive it or not but ** got the Original man to make more of the Skipper's about a year or so ago and I like to died when I seen all of those NEW SKIPPER's sitting on his shelves.
Lon |
Legend
Junior Member
Username: Legend
Post Number: 37
Registered: 12-2002
| | Posted on Thursday, April 15, 2004 - 10:27 am: |
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Hi Jeff...
A few comments.
You mentioned:
"If it indeed does 450-470 watts output, no one would ever know if you backed the power down to 300 watts."
The amp has 4 8950's. One driving three. It does 450-470 SSB, but that doesn't mean I intend to run it that way. I was just stating the full output of the amp, asking if that was normal. Maybe that way, I'd know if my tubes are new, as I was told when I bought it.
You also mentioned:
"The A/M-SSB switch has nothing to do with it sticking. If you will notice, when it is in the SSB position, the relay will be delayed a bit during its "unkey" cycle. There is a capacitor in circuit that has to unload when there is no longer any RF power present. Basically, all this capacitor does is slow the relays down and keep them from chattering while in the SSB mode."
Yes... I am totally aware of everything stated there. However, this is not my problem. The amp will be delivering output just fine, when all of a sudden, my power drops out, down to barefoot. When I try to key the amp after that, I don't hear the relay like I normally do, and it only keys up barefoot power. But... if I key it a few times, it will once again key up power.
I have no way of cleaning the two relays that are self-contained. They would have to be replaced. There is one relay (out of a total of three) that plugs into a socket. That one looks as if I can take the cover off, but I do not know if that is the one causing the problem, which is the main reason I need a tech that knows these amps well, to help me out.
And finally, you said:
"Next, check the little nuts and bolts that are used to mount the transformer to the chassis. They may be a bit loose."
The first thing I did when I received the amp, was go through it and tighten up all the loose hardware. The screws on the transformer were loose when I got it, but I tightened them up. The buzzing problem did not start until after I had used the amp for awhile. It got progressively worse, but does not go over the air. It's just annoying, and I know that this level of transformer noise is not normal, or coming from vibration due to loose screws.
That is another reason I'm trying to get a tech to help me here. Exacty what DOES a transformer do when it is getting ready to go south? Does it make anymore noise than usual?
Everything in my set up is excellent, SWR wise. Perfectly flat, in fact. I have the amp tuned to run at optimum efficiency, so it's not an abuse issue.
Thank you for your efforts to help. I definitley appreciate it Jeff.
Now... if i can get a tech to advise me as to which relay is the most likely one to be causing my output to suddenly drop out during transmit. And sometimes after I unkey with power on, it will fail to key with power when I key up afterward. The reason I think it is a relay, is because it clicks when it keys up power, but doesn't click when it fails. So, I figure it is either a relay, or a component that feeds a relay.
Also, does a transformer start to buzz worse and worse, just before it goes?
Techs... Hello? Please help. I'd like to get this problem licked.
Thanks in advance. |
Legend
Junior Member
Username: Legend
Post Number: 38
Registered: 12-2002
| | Posted on Thursday, April 15, 2004 - 12:49 pm: |
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Since my last post a couple of ours ago, I think I have isolated the problem. My amp keeps dropping out unless I turn on the Receive amp. If I leave my radio keyed, the output jumps right up when I click the receive amp on. Does this make any sense?
But... after doing that a few times, my amp will not even key up any power regardless of the position of ANY switch. It's as if the relay responsible for delivering power has worn out.
I can hear a click when I key the amp, but now, only barefoot power comes out. If I mess around with it for a while, the power will TRY to come on. It will jump up to proper output for a second, and then drop back to barefoot. It is not the tubes. It is definitely a bad connection, be it a relay, or other.
There are two yellow colored relays, and one clear plastic one, which plugs into a socket. The yellow relays are numbered:
AMF- Potter & Brumfield
R50-E0043-1
Techs (or anybody that is very familiar with this amp), could you help me out here?
Thanks |
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