'76 DR105 problem

[Buzzardstein76]

on my 1976 DR105, my 470 Ohm 10W resistor keeps unsoldering itself and coming loose. it is the original green one. the 100 ohm 5W one seems to be ok (original green one, too). i have resoldered these resistors at their junction a few times and after about 15 minutes of loud jamming, it comes loose. is this a bad resistor? I didnt have my multimeter with me to check. tonight the 470 ohm came off from both ends.

[mhuss]

The resistor is overheating, hence the melting solder problem. I suspect it is also lighter green in the middle and the printing has faded a bit.

Are the Mains/HT fuses the correct values? (max 5A mains, 3A HT) Check the output tubes to make sure they're not red-plating. If you have a meter, can you measure the voltage being dropped across this resistor when the amp is on and idling?

--mark

[Dr.HI-TONE]

I would check the resistance of the 470R if within spec. I would start looking upstream and downstream of it.

Mark beat me to the punch..........listen to him!

[Buzzardstein76]

will any resistor work as long as the values match or do i need a specific type?

[mikhailwatt]

will any resistor work as long as the values match or do i need a specific type?

Any type will "work" but flameproof wirewound would be my recommendation.

http://www.vishay.com/docs/30215/cw.pdf

[Buzzardstein76]

the tubes seems fine. no redplating. the resistor value was faded pretty bad. the amp has two 4 amp fuses in it. a slow blow in the mains and a fast blow in the HT. i will change the HT to a 3 amp. i changed the 470 ohm and the 100 ohm resistors, too. i dont have a cab here at the house, so i will not be able to test it until tomorrow night.