|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
Dear All,I have recently purchased a ARC CL30. I have done some research on biasing this amp. Here is the method I can find so far.
"After the retubing of this equipment You need to set only the 6550s
bias. After You put the new valves, check the voltages between TP1
and TP2. You have to set 32.5mV, with RV2. After this action check
TP1 and TP5, it must be same. If no, RV1 can change it. Than the left
channel ready. For the right channel: check between TP3 and TP4, and
check TP3 and TP6. The difference can eliminate with the right
channel RV1.
As I know there is only one potenciometer to set the bias, and You
must use matched quads for the proper working."However, I have no idea where are the Testing Points is? Would anyone kindly point out the testing points?
Follow Ups:
Here is the top of the motherboard. Yes, the potenciometer is clearly to be located.
The 2nd hand shops claims it is the latest patch. The front panel print with CL30 rather than Classic 30. The corners of the panel are round. Anyone know if the internal circuit has any change?
Prost,Not to scare the bee-jeebers out of you, but unless you've done biasing before and really know where and how to bias an amp---I'd let an amp tech do it.
There are dire consequences if you do not do this operation correctly. Maybe, watch a tech that knows AR's do it, the first time. But, excess fiddling may lead to regrets.
Hi Steve,Thanks for your advise.
I also own a VT100 MKIII. I have experience of retubing. I have no problem of biasing the VT100 because it has a very obvious measuring point.
I love to change tubes to seek for the best sound like. If I have to do the bias each time with a amp tech. Yes it is safter, but I will certainly lose the fun from retubing.
Prost,Probably best to get the owner's manual, a good book on basic tube maintenance, a DVM, and maybe a practice amp to learn on. Maybe, a low output integrated amp for the bedroom.
You sure would hate to fry that AR while learning the in-&-outs of biasing. Biasing tends to be an art, rather than an exact science. You can bias the amp to a subtle tone range depending on the brand of 6550 and vintage of tube you are using.
But, I'll warn you---a 6550 amp uses a lot of voltage and potential current. So, the potential for big-time harm---if the settings are not within the proper window is great. And in some amps, it doesn't take much time for damage to be done. Plus, the high voltage these amps use, puts you at risk if you need to measure plate voltages to get the idle bias point into the plate dissipation window.
Just my 2¢ worth.
This post is made possible by the generous support of people like you and our sponsors: