Hi all,
I've a B&K 707 on the bench for servicing, was given to me by an old tv/radio tech.
I've already replaced caps and resistors since they were out of range, calibrated the unit sucessfully, so I think is working fine. I haven't replaced the 83 rectifier with a pair of SS 1n4007 for keeping it all original...
Now, if I test a 12AU7(ECC82) or 12AT7(ECC81) they measure fine on the meter,
If I test a 12AX7(ECC83) (tried some new JJ / EH and also some Nos Siemens) I read around 25 (chart states * good if 22 or more) still a 22 on 120 scale seems odd .
So, I want to ask you guys, is a B&K an accurate tester? It's worth keeping ?
I don't understand how can you measure a 12AU7 and a 12AT7 (different beasts)by just turn the shunt by 1 cent ? 75 vs 74
Also, how can you measure a 12AX7 on it?
Can someone otherwise suggest me a DIY project ?
Thanks
I've a B&K 707 on the bench for servicing, was given to me by an old tv/radio tech.
I've already replaced caps and resistors since they were out of range, calibrated the unit sucessfully, so I think is working fine. I haven't replaced the 83 rectifier with a pair of SS 1n4007 for keeping it all original...
Now, if I test a 12AU7(ECC82) or 12AT7(ECC81) they measure fine on the meter,
If I test a 12AX7(ECC83) (tried some new JJ / EH and also some Nos Siemens) I read around 25 (chart states * good if 22 or more) still a 22 on 120 scale seems odd .
So, I want to ask you guys, is a B&K an accurate tester? It's worth keeping ?
I don't understand how can you measure a 12AU7 and a 12AT7 (different beasts)by just turn the shunt by 1 cent ? 75 vs 74
Also, how can you measure a 12AX7 on it?
Can someone otherwise suggest me a DIY project ?
Thanks
Attachments
First of all I must admit I like B&K test equipment I have a B&K 467 CRT tube tester /analyzer , their equipment in quality is a step up from standard builds of the day and that includes Hickock,s .
If I was American and lived in America I would buy that n model or one like it from the B&K range , don't put it down my CRT tube tester still works okay and if push came to shove it can be converted to a tube tester .
Read-
TubeSound >> Blog Archive >> B&K 700 & 707 tube tester
Please scroll down to the "Red " section commenting on Jet-Check mu sockets they are meant for a quick test --okay there are more technically superior tube testers with more control but I have seen the problems some of them have when repairing them ,It took me months to go through my old AVO VCM MK4 to get it "up to scratch " .
Here you can download the instruction manual &the tube chart & schematic in PDF.-
Bama Manual Archive
If I was American and lived in America I would buy that n model or one like it from the B&K range , don't put it down my CRT tube tester still works okay and if push came to shove it can be converted to a tube tester .
Read-
TubeSound >> Blog Archive >> B&K 700 & 707 tube tester
Please scroll down to the "Red " section commenting on Jet-Check mu sockets they are meant for a quick test --okay there are more technically superior tube testers with more control but I have seen the problems some of them have when repairing them ,It took me months to go through my old AVO VCM MK4 to get it "up to scratch " .
Here you can download the instruction manual &the tube chart & schematic in PDF.-
Bama Manual Archive
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Thank for your reply
I've already visited bama, same documentation as mine, same calibration procedure, the tester is ok.
The "tubesound" page talks about a 12AX7 mod, same as described here :
Antique Radio Forums • View topic - 12AX7 Test Modification For B&K 707
So I may keep this instrument since is in good condition and this instrument is fast for the purpose of testing stash of old tubes which need only a pass / reject test
BTW I would really appreciate if someone can suggest me a good DIY project for testing tubes, I mostly service audio parts so matching tubes ecc it's important to me.
I generally set up a bench test for the tubes I'm matching but it takes too much time.
I've already visited bama, same documentation as mine, same calibration procedure, the tester is ok.
The "tubesound" page talks about a 12AX7 mod, same as described here :
Antique Radio Forums • View topic - 12AX7 Test Modification For B&K 707
So I may keep this instrument since is in good condition and this instrument is fast for the purpose of testing stash of old tubes which need only a pass / reject test
BTW I would really appreciate if someone can suggest me a good DIY project for testing tubes, I mostly service audio parts so matching tubes ecc it's important to me.
I generally set up a bench test for the tubes I'm matching but it takes too much time.