Search found 14 matches
- Fri Sep 09, 2016 5:57 pm
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
Sounds interesting. Make sure it's not too noisy, though. SMPS are very noisy. Also, how do you plan to have your filaments powered? Use the same DC power section (before it is raised by switched mode for HT) or use a separate 12VDC? The Eddy Van Halen trick might be good too. Ideally, it should low...
- Fri Sep 09, 2016 2:50 pm
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
If you take the voltages posted above, the idle current drawn by the output PP is about 20mA. Each triode in the preamp can be reckoned at about 1mA. So that's 24 or 25 mA for idle. Don't know about peak. It probably doesn't change much for the preamp section and might increase a bit for the output ...
- Wed Jan 20, 2016 6:19 pm
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
What schematic did you use? Matec's HTM1?
May be it is the 150V HT that is too low. What is your DC voltage at the power stage?
Have a look at the voltages on the attached picture. This will give you an idea.
May be it is the 150V HT that is too low. What is your DC voltage at the power stage?
Have a look at the voltages on the attached picture. This will give you an idea.
- Mon Jan 18, 2016 7:18 am
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
Nice build
How does it sound? Do you have PCB layout?
What TR did you use? I can see a small Hammond for output, but what is the power transformer?
How does it sound? Do you have PCB layout?
What TR did you use? I can see a small Hammond for output, but what is the power transformer?
- Fri Jun 12, 2015 9:52 am
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
Hi everyone, Odrpol, your output tube V3 draws too much current, about 20 mA per triode and that is way too much for 12AU7. Calculated dissipation for each triode is about 5 watts, but it should not go over 2.5 W. If you want more output power, use ECC99 instead. It's a good replacement tube for 12A...
- Sat Jun 06, 2015 8:29 am
- Forum: Marshall Discussion
- Topic: Seeking troubleshooting tips on my Marshall JTM30
- Replies: 27
- Views: 6486
Re: Seeking troubleshooting tips on my Marshall JTM30
Yes, you are right. I knew I was wrong at the minute I posted this. A 30V drop with about 30 mA per leg would make a 1k difference in DC resistance. That's definitely too high.
Too bad for the iron.
Too bad for the iron.
- Sat Jun 06, 2015 8:26 am
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
About the connection of OT transformer – I have read in the datasheet of 12AU7, that the maximum rating of anode voltage is 300 V, at main 294 V I’m afraid that is to nearest from maximum, following datasheet, and I connect the OT to lower tension to get about 250V at the anode this valve. At datas...
- Fri Jun 05, 2015 8:15 am
- Forum: Marshall Discussion
- Topic: Seeking troubleshooting tips on my Marshall JTM30
- Replies: 27
- Views: 6486
Re: Seeking troubleshooting tips on my Marshall JTM30
Oh I see now. Sorry about the mismatched tubes. I was wrong. If you always get the same unbalanced voltages always lower on the same side, that probably means your OT is part of the problem, if any. What I mean by "if any" is that it may be due to a difference in DC resistance between both primary w...
- Fri Jun 05, 2015 7:05 am
- Forum: Marshall Discussion
- Topic: Anderton '64 reissue JTM145 - any info?
- Replies: 442
- Views: 119115
Re: Anderton '64 reissue JTM145 - any info?
Hi there, Yes, as Matec said, something is definitely wrong about your measured voltages. Aso, you should stick to Matec's original schematic or even use his HTM1 schematic which has best of both worlds. The way your output transformer center tap is connected to a lower B+ is not correct to me. :roll:
- Fri Jun 05, 2015 7:00 am
- Forum: Marshall Discussion
- Topic: Seeking troubleshooting tips on my Marshall JTM30
- Replies: 27
- Views: 6486
Re: Seeking troubleshooting tips on my Marshall JTM30
Different plate voltages just mean output tubes are not matched perfectly, but that should not prevent the amp from working.
As for the popping noise when you smack your amp, may be preamp tubes become more microphonic when they heat up?
As for the popping noise when you smack your amp, may be preamp tubes become more microphonic when they heat up?
- Wed May 27, 2015 6:20 pm
- Forum: Marshall Discussion
- Topic: Seeking troubleshooting tips on my Marshall JTM30
- Replies: 27
- Views: 6486
Re: Seeking troubleshooting tips on my Marshall JTM30
I quickly re-read this topic and, maybe I have missed something, but it seems that you have put back two new caps without removing both straps where the diode bridge used to be, and without installing a new bridge. If so, you are filtering 6.3 VAC without first rectifying it, and that's not good at ...
- Wed May 27, 2015 5:06 pm
- Forum: Marshall Discussion
- Topic: Seeking troubleshooting tips on my Marshall JTM30
- Replies: 27
- Views: 6486
Re: Seeking troubleshooting tips on my Marshall JTM30
At first glance, it seems that previous owner or someone else has removed the DC filtering part for preamp heaters and chose to power all heaters (preamp and output) with AC right from the PT secondary. That's why the diode bridge and both filtering caps C122 and C123 have been removed. Now, why did...
- Sun May 24, 2015 2:55 pm
- Forum: Marshall Discussion
- Topic: Wanted by internal images of JMP1H or C
- Replies: 7
- Views: 4045
Re: Wanted by internal images of JMP1H or C
Hey Matec,
Check you PM mail, there's a cool pdf file.
Check you PM mail, there's a cool pdf file.
- Fri May 08, 2015 5:25 pm
- Forum: Marshall Discussion
- Topic: JTM1 Impedance Issue
- Replies: 41
- Views: 9203
Re: JTM1 Impedance Issue
Hi, This is my first post here, though I've been following and reading a lot about JTM1 and other builds for some time. Littlewyan, why not have a look at this OT from OEP: http://www.oep.co.uk/pdf/N35A002F%20issue%205.pdf It is sold for about 15 quid VAT and shipping included in UK. You can find it...