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Post by Eduardo Wobblechops on May 2, 2019 18:48:57 GMT
Getting there, it's been a mission lol. Will be worth it though.
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Post by The Brookmeister on May 2, 2019 20:52:16 GMT
ffs what a faff
LOL
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Post by Eduardo Wobblechops on May 2, 2019 21:15:35 GMT
Sharrup you.
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Post by Eduardo Wobblechops on May 4, 2019 16:46:25 GMT
Pretty much done now, or at least as far as I can go until I get the toroids Amethyst are making for me, then it's just a case of wiring up the filament supplies and Bob's yer mother's brother. Four filament supplies added, again not part of the original kit, but these will make a significant improvement to SQ-   |
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Post by dubulup on May 24, 2019 15:02:57 GMT
I am a fan of Transcendent Sound; has this amp been fired up?
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Post by Eduardo Wobblechops on May 25, 2019 22:10:49 GMT
Yes, has a fault which I’m hunting for, hopefully get time for a good look tomorrow.
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Post by MartinT on May 25, 2019 22:36:58 GMT
Are all the power supplies up and running, Ali?
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Post by Eduardo Wobblechops on May 26, 2019 4:35:21 GMT
It’s blowing the fuse on one of the pair of 300b’s- the neg rail is earthed somewhere. Same on both monos so at least I’m consistent lol.
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Post by dubulup on May 26, 2019 11:33:05 GMT
I scratch built a Son of the Beast (15W OTL) from Bruce Rozenblit's book Tube's and Circuits (2012) and the PSU looks very similar for B+/-. Full bridge and CLC filters stacked. Looking at your photos, I see the power transformer secondaries connected to the rectifier bridge (T7 ORG/RED) and then to the first filter caps on the DC side. I can spot another secondary (BLK) on C2+...however that is the last PT secondary I can spot, where does the 4th wire connect? Also what is the secondary voltage of this PT?
I had an issue when my SOB OTL would blow the neg tube pair fuse after 15-45 seconds after power on...it ended up being I referenced the fixed bias incorrectly. I can't really see what is going on around the baby bias transformer. I assume your mains are 230-240? More pictures would be nice to see if you have some more to share.
I assume the toroidal transformers from Amethyst are for your 300B heaters and input/driver filaments, all other circuits working correctly? I like the soft start idea. K&K provides great products and support. I recently built Bruce's cathode follower amplifier with Lundahl transformers (supplied from K&K) and it sounds absolutely stunning.
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Post by Eduardo Wobblechops on May 26, 2019 20:26:31 GMT
Yes mains 240. PT has two 115v centre tapped secondaries, hence the three wires.
Correct, new transformers have 4 9v secondaries that drive the filament supplies, and a 6v for the small valves- also runs the time delay board.
There is a fuse for each pair of 300b’s, one on the +315v rail, other on -315v, same as SoB I think?
Fuse on -ve rail is blowing as soon as delay board kicks in, so problem is on that rail somewhere.
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Post by Firebottle on May 27, 2019 7:32:43 GMT
Possibly daft question, have you checked that the 4 heater supply secondaries are all isolated from one another?
Heater supply mountings all isolated?
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Post by Eduardo Wobblechops on May 27, 2019 7:39:17 GMT
Yes all ok Alan, the filament supplies work fine.
EDIT. You were right Alan. What a twonk I am lol. I used tag strips to connect heater secondaries to filament supply cables, forgetting that the centre tag is bolted to the chassis..
Confused they were still working, but sorted now in any case, no fuses blowing and PS voltages all check out.
Thanks for the assistance gents, much appreciated.
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Post by Eduardo Wobblechops on May 27, 2019 9:11:10 GMT
I scratch built a Son of the Beast (15W OTL) from Bruce Rozenblit's book Tube's and Circuits (2012) and the PSU looks very similar for B+/-. Full bridge and CLC filters stacked. Looking at your photos, I see the power transformer secondaries connected to the rectifier bridge (T7 ORG/RED) and then to the first filter caps on the DC side. I can spot another secondary (BLK) on C2+...however that is the last PT secondary I can spot, where does the 4th wire connect? Also what is the secondary voltage of this PT? I had an issue when my SOB OTL would blow the neg tube pair fuse after 15-45 seconds after power on...it ended up being I referenced the fixed bias incorrectly. I can't really see what is going on around the baby bias transformer. I assume your mains are 230-240? More pictures would be nice to see if you have some more to share. I assume the toroidal transformers from Amethyst are for your 300B heaters and input/driver filaments, all other circuits working correctly? I like the soft start idea. K&K provides great products and support. I recently built Bruce's cathode follower amplifier with Lundahl transformers (supplied from K&K) and it sounds absolutely stunning. How does the CF compare to the OTL? |
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Post by dubulup on May 27, 2019 13:08:49 GMT
EXCELLENT NEWS! Patiently waiting for some impressions...
during my test benching the standard CFA (barely 3W - single PS, 6550, and Electron 1 UBT-1 transformer) didn't really hold a flame to the SOB...maybe blame some of it on "break-in". The final configuration is dual mono PS, KT150 output tubes, and LL1623 transformers. The CFA performs so well it is now driving my KEF reference one 85dB speakers with a passive pre-amp. It tested just under 4W, so this absolutely doesn't make any sense to me?! The SOB has extremely anemic bass response into that load; which dips down to 2-3ohms.
I don't want to cloud this thread with cathode following OTC amp talk...I do want to find a way to post pictures (photobucket seems to be "restricted" with too many pics...seems something has changed) here and I'll start a thread.
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Post by The Brookmeister on May 27, 2019 15:37:36 GMT
Will it be playing this weekend fella?
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Post by Eduardo Wobblechops on May 27, 2019 15:48:24 GMT
Hope so mate. Need to find a dodgy solder joint on one, if I get that sorted they’ll be there. Also just picked up a pair of NCore Monoblocks, I’ll bring them as well.
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Post by MartinT on May 27, 2019 15:50:45 GMT
Damn, would love to hear them running.
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Post by Eduardo Wobblechops on May 27, 2019 15:53:48 GMT
EXCELLENT NEWS! Patiently waiting for some impressions... during my test benching the standard CFA (barely 3W - single PS, 6550, and Electron 1 UBT-1 transformer) didn't really hold a flame to the SOB...maybe blame some of it on "break-in". The final configuration is dual mono PS, KT150 output tubes, and LL1623 transformers. The CFA performs so well it is now driving my KEF reference one 85dB speakers with a passive pre-amp. It tested just under 4W, so this absolutely doesn't make any sense to me?! The SOB has extremely anemic bass response into that load; which dips down to 2-3ohms. I don't want to cloud this thread with cathode following OTC amp talk...I do want to find a way to post pictures (photobucket seems to be "restricted" with too many pics...seems something has changed) here and I'll start a thread. Cool, some pics would be good. Well got them plumbed in to the main system and... mucho hum and one started playing very quietly, most likely a bad solder joint, so I’ll have to go through it again. the hum isn’t the amps, they are quiet if I disconnect the inputs, so I’ll need to find the cause of that too. Had enough for today, not stopped since 8.00am so bugger it, they can wait. Plugged the NCores in instead. :-) |
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Post by Eduardo Wobblechops on May 27, 2019 15:54:58 GMT
Damn, would love to hear them running. Come to Owston. :-) |
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Post by MartinT on May 27, 2019 16:00:12 GMT
Checks distance...
Probably not!
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