|
|
Post by husker on Aug 28, 2008 14:37:50 GMT -5
The Tram D201A that I like to use ( the cleanest of the two) is very cold blooded. What I mean is it takes a bit to warm up to do a proper transmit. After a good warm up, say 20 minutes it sounds awesome and swings very nicely. But after a bit of use it kinda gets flaky. The transmit will not really work, when you key it the wattage will only do about 1-1 1/2 watts and just stay there, no movement for swing etc. I have to power it down then back up and it works again for a while then the same thing. Any ideas?  ? thanks folks |
|
Sandbagger
Administrator/The Boss 
Posts: 6,247 
|
Post by Sandbagger on Aug 28, 2008 18:42:04 GMT -5
The Tram D201A that I like to use ( the cleanest of the two) is very cold blooded. What I mean is it takes a bit to warm up to do a proper transmit. After a good warm up, say 20 minutes it sounds awesome and swings very nicely. But after a bit of use it kinda gets flaky. The transmit will not really work, when you key it the wattage will only do about 1-1 1/2 watts and just stay there, no movement for swing etc. I have to power it down then back up and it works again for a while then the same thing. Any ideas? ? thanks folks Most likely a weak tube or a resistor that's become heat sensitive. Or, possibly a cold solder connection on or near one of the hot resistors or tube socket. |
|
|
|
Post by husker on Aug 28, 2008 19:52:55 GMT -5
Ok, so I went through this thing tonight with a fine tooth comb! I found 11 resistors that need to be replaced( they are CHARRED) and I think I found the real issue..the big 3 way CAP ( 40x450) is leaking like a bad dog....ok, so now I have a question for the experienced guys....
Greg has replacement caps exactly like these..OR should I use cheaper newer caps? Money is not really the issue and I would LOVE to have this radio look stock...but if I get these silver caps from Barkett how long will they last???
thanks again guys
oh and to make it ever stranger, someone put a 47ufx450v cap on the bottom of the big three way...I wonder if there was an issue and someone jsut patched it to keep this radio running long enough for some sucker ( me) to buy it off Ebay??
Bob
|
|
|
|
Post by mark4 on Aug 28, 2008 21:04:28 GMT -5
Sounds like a great candidate for a 100,000 mile tune-up!
And to answer your question-how long will they last.
No telling? I have used the twist lock caps to keep my radios stock. Some have lasted 6 months and others going strong for years. There have been some problems with them in the past.
Called up the manf. and told them the high failure rate and sent them back for analysis. They tell me they have resolved the issue.
I don't modify chassis to accommodate a 2 section cap. Or cram them in the bottom of the chassis. But it's all up to the owner.
|
|
|
|
Post by husker on Sept 2, 2008 22:23:04 GMT -5
Ok, I went through and replaced any resister that looked..well quite frankly old and or burnt. I went through about 7 tonight and I am getting another 6 tomorrow. But so far I have this old girl rockin! She sounds awesome and on-air reports were.. "wow..that thing sounds incredible" I figure I might as well replace a few more that look burnt or charred (hard to find a few of these suckers, but I get them from a surplus place in Omaha that has stock of the older bigger resistors so the look is the same) after I get them tomorrow. After I get this one done I will start on the other D201A that is way more of a project.
|
|
|
|
Post by 2600 on Sept 4, 2008 1:27:51 GMT -5
Our general rule for replacing the chronically-overheated resistors in the D201 radios is double or more the original power rating.
A 2-Watt resistor gets replaced by a 5-Watt. 1-Watt part with a 2-Watt. Only two or three half-Watt parts are on the list, but the thickness of the lead wires may prevent you from replacing them with a part larger than one Watt rating. Unless you (carefully) ream the holes in the pcb first.
I remember a customer years ago who figured out that standing those resistors up on long leads would improve air flow around them. So he left the lead wires really long on the replacements. Trouble was, he underestimated the leverage they would put onto the foil traces under the pc board.
The leverage caused the adhesive under the foils to come loose. Looked a bit odd if you saw the inside of the radio when it was picked up or jostled. A dozen or so resistors all doing the 'hula', rocking back and forth inside the radio.
Standing the part up on a quarter-inch or so of additional lead length will improve air flow around the hot resistors, but much longer than this can create a problem with that 'leverage' issue.
73
|
|
|
|
Post by husker on Sept 4, 2008 21:07:34 GMT -5
That's exactly what I did, I gave them an extra room for air flow...
|
|
|
|
Post by husker on Sept 7, 2008 10:29:58 GMT -5
ok, I have done a lot of changes, replaced caps ( waiting on a few that are on order) and replaced alot of resistors that were blistered or charred! THe radio is working beautiful, BUT...there is a very slight 60 cycle hum...very slight, but I can hear it..thoughts?? Could it be one of the 4uf caps that I have on order???
thanks
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 8, 2008 7:21:32 GMT -5
ok, I have done a lot of changes, replaced caps ( waiting on a few that are on order) and replaced alot of resistors that were blistered or charred! THe radio is working beautiful, BUT...there is a very slight 60 cycle hum...very slight, but I can hear it..thoughts?? Could it be one of the 4uf caps that I have on order??? thanks I have the same issue on both my Trams and with most of the ones I've worked on. Since I've never had a "Mint" one back in the day to compare to, I don't know whether that slight background hum is normal (sort of like the guitar amps from the day), that's being picked up from a floating ground or something, or a sign of a further issue. The hum is only noticable when the volume is all the way down, not seen on transmit, and once the volume is advanced, is not noticable on the receive audio. Might just be a microphonic tube, or maybe a bypass cap. Certainly not the filters as they've all been changed. |
|
|
|
Post by husker on Sept 8, 2008 7:53:20 GMT -5
exactly, just a very slight back ground, not heard in transmit, and it does tend to go away when you advanced the vol knob. FOlks just love they way this radio sounds on the air. There is nothing like a good running tube radio! Thanks to all of you for the help to make this thing run beautiful.
|
|
?
