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tram d201 blows main fuse on back..help..

T

troyota

W9WDX Amateur Radio Club Member
May 9, 2007
104
5
28
i bought a tram d201 23 channel. it looks great and worked great with outstanding receive and transmit. i have had it a month or so now. i hooked it up last night and talked on it and got great audio reports as always.
anyway i got busy doing paperwork and was just letting it sit there and receive. listning to the locals, then all the sudden it went quiet, i looked up and it was not on anymore. so i checked the rear fuse and it was blown, so i put another in it and it blows it instantly.
i have checked all tubes with a tube tester for shorts and emmission. all are good no grid leakage either. looking at the board i see no apparent damage, or burnt components. any ideas that come to mind?
thank you
 

Sounds like soumething in the power supply went south.
Start by pulling the BA board. That is the up-right board by the audio tube. I seen this board go bad and cause shorts. The three caps on that board often fail.
Then check the 40x3 and 10x4 caps. Along with the diodes.
 
Beware of tube testers on power tubes. They usually don't put the tubes into the dissipation the radio does.

As mentioned, look for electrolytics that show signs of heat. The plate blocking capacitor in the final can screw up also. Check for chaffed wiring. See if the thing runs without the BA board and/or 6L6s. That BA board gets a cooking from the audio power amp. Those caps aren't rated to work properly while being cooked.
 
first off thanks for the replys. here we go. with the ba board out, still blows fuse. with all tubes removed still blows fuse. i did notice on the small cable inside (rca cable on one end) the end that goes to the top of the crystal channel selector shows shorted with continuity tester. i can unplug it and the crystal channel connector board tests good, (no continuity) the cable still tests connected tho. i have looked around on the board but no visible problems. thanks for the help so far guys any more thoughts?
 
You need to disconnect the wire from the 3x40 cap that feeds HV to the radio and see if it still blows the fuse. Leave the tubes out when you do this also. You can see where to do this on the schematic at the link posted. It is the 410 volt source in the lower right hand side of the schematic. I'll bet either one or both of the caps or a bridge rectifier is shorted. Do the caps have any corrosion oozing out of them around the connections? Be careful in there, HV and AC can change your outlook on life.

http://www.cbtricks.com/radios/tram/d201/graphics/tram_d201_sch.pdf
 
i assume its the tallest large silver cap right in front of the large power supply correct? the manual refers to it as c5. it does have corrosion on one connection on the bottom of it. i will find the power source wire and dissconnect it then try it. it is not showing continuity or shorted to ground on my meter tho.


it appears the one you are talking about is the one marked with a triangle on the cap, which is connected with a strap to the square sign pin too. on the bottom of the cap its the small red and blue wire, and the large blue wire. the small red wire appears to go to the switch, the large blue wire goes to the smaller transformer i think. the smaller blue wire goes to the connection point #13 on the board. just want to make sure i get the right one.
thank you
 
Last edited:
Yes, it is C5. If you look there should be two 47 ohm (yellow, violet, black) 2 watt resistors tied to the half moon connection on the can. Beside each connection to the can is a symbol (square, triangle, or half moon) to tell which section is which. You can unhook the supply line to the can and see if it still blows the fuse. If it does you have a something shorted between that and the power cord. It is just a case of following it back until you can plug it in and the fuse does not blow. The last thing you took out of circuit has the bad component in it. Remember to be careful.........it will hurt you.
 
ok the resistors are on the top of the board. the half moon is connected to them from underneath. is this the supply line? if so, it still blows fuse. i unhooked it at the board between the can and resistors.
thanks for your help so far.
 
On C5 you will notice that one leg is by itself and the other two are connected together.
Just unhook the single leg and see if it has a short to ground. If not reconnect and unhook the other two legs. As BC said it is 3 40 UF caps in one. Two legs are tied together for 80 mics. As you test each leg and find them not be shorted, then I would start with the HV transformer wires. If it still shorts the fuse go to the low voltage windings.

Make sure the wires on the power switch have not shorted to the ground wire.

And again as BC said, Please be carefull in there. It is over 400 volts.
 
ok thanks again guys, it doesnt seem to be the cap. i ran out of fuses, till i get to the store. can i check with a continuity tester to ground, that would work correct? i did have a fuse whan i unhooked the lead on the cap that is not connected to the other one (40 uf) it blew the fuse. then i un hooked the 2 red wires from the hv tranformer, it blew the fuse. the red wires dont show shorted to ground with my tester tho. bad thing is that was my last fuse less than 5 amp anyway. hmmm... i could put in a 30 amp and get the fireworks show i guess.......LOL.... not happening guys calm down..LOL
anyway i tested the green wires out of the hv transformer and they are showing short to ground with my tester. the black wire from the hv tranformer is not showing short to ground. is that right???? BTW these wires are not unhooked yet. maybe thats why.
thanks troy
 
ok i unhooked the green wires from the hv transformer. now not shorted to ground, so now the green and the red are unhooked. plugged in and the fuse didnt blow. i could hear the normal transformer humm so i hope the hv transformer is still good. any more ideas now?
thanks guys
 
another thing all the brown and yellow wires are shorted to ground on the bottom of the audio board
 
ok i guess i was grasping at straws. i realize the brown and yellow are the grounds for the tubes.
i went back to the basics and found a diode opened. i replaced it and its working for the time being anyway. gonna let it warm in awhile and see how it does.
thanks to all that helped
 
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