warwickhunt Posted November 13, 2022 Author Share Posted November 13, 2022 11 minutes ago, Bill Fitzmaurice said: Based on the size I agree. You may find numbers on it if you pull it. Sadly the original was fritzed (no visible 'useful' info) and the replacement wasn't up to the job so I'm back to square one. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 Guess what I found; I forgot I'd photographed it first time! 2 Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 14, 2022 Share Posted November 14, 2022 Looking at what has happened to that transformer, and the fact that its replacement has also died (has it displayed the same overheating symptoms?) would suggest to me that there is a fault somewhere in the pre-amp that is causing this and you/your tech will need to sort this out as well as replacing the transformer. 1 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 No warning leading to either transformer failing (oddly it never exhibited any of the issues you had, when I used it). I'm waiting to get the amp back from the Tech but the faint whiff of smoke when it died on me leads me to assume it is the same issue... which means there is an underlying problem. I'd like to hope it is a fault and not a design oversight! The Tech who fitted the last transformer has offered a full refund but as he couldn't identify what lead to the failure he hasn't taken up the job of fitting the next transformer (if I can find a suitable one). Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 14, 2022 Share Posted November 14, 2022 28 minutes ago, warwickhunt said: No warning leading to either transformer failing (oddly it never exhibited any of the issues you had, when I used it). I'm waiting to get the amp back from the Tech but the faint whiff of smoke when it died on me leads me to assume it is the same issue... which means there is an underlying problem. I'd like to hope it is a fault and not a design oversight! The Tech who fitted the last transformer has offered a full refund but as he couldn't identify what lead to the failure he hasn't taken up the job of fitting the next transformer (if I can find a suitable one). Considering that the amp has run for at least 15 years before this problem occurred and then has occurred twice in a short period of time, would suggest to be a new fault has developed somewhere else in the pre-amp. 2 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 I agree or (and I don't have sufficient knowledge but applying common sense) something 'after' the preamp is causing some form of feedback/reverse issue. It could also be a case of the 17 year old transformer had failed but that the new one wasn't the correct spec. Quote Link to comment Share on other sites More sharing options...
TimR Posted November 14, 2022 Share Posted November 14, 2022 (edited) 0.8amps at 12V is tiny. Stick it into any amp repair shop and they'll fix your issue and fit a replacement. 9.6 VA (Watts) must be preamp. I think you're overthinking this. A transformer is a transformer. Basic component. Edited November 14, 2022 by TimR Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 2 minutes ago, TimR said: 0.8amps at 12V is tiny. Stick it into any amp repair shop and they'll fix your issue and fit a replacement. 9.6 VA (Watts) must be preamp. I think you're overthinking this. A transformer is a transformer. Basic component. I did. I've had it repaired once... with a basic component and it worked flawlessly for <5 hours! Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted November 14, 2022 Share Posted November 14, 2022 12 minutes ago, TimR said: 0.8amps at 12V is tiny. Stick it into any amp repair shop and they'll fix your issue and fit a replacement. 9.6 VA (Watts) must be preamp. I think you're overthinking this. A transformer is a transformer. Basic component. That will be the secondary for the heater filaments, connected in series. That’s where the ‘12’ in 12AX7 comes from. There should be more than enough there to run 3 preamp valves. I can’t read the label well enough to work out the spec for the HT secondary, and so far I’ve got nowhere Googling bits of the text printed on it. 2 Quote Link to comment Share on other sites More sharing options...
TimR Posted November 14, 2022 Share Posted November 14, 2022 It's a Noratel transformer. Maybe they have some records. https://www.noratel.com/market-segments/audio/ 1 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 6 minutes ago, TimR said: It's a Noratel transformer. Maybe they have some records. https://www.noratel.com/market-segments/audio/ Blimey good find! Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 14, 2022 Share Posted November 14, 2022 Unfortunately it may well be custom wound as I think I can spot the words "Tech Bass" on the side and none of the codes appear to correspond with any of those on the 12V 0.8A standard transformer spec sheet. I wonder if the two secondaries are different for the pre-amp circuit and the valve heaters? Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 5 minutes ago, BigRedX said: Unfortunately it may well be custom wound as I think I can spot the words "Tech Bass" on the side and none of the codes appear to correspond with any of those on the 12V 0.8A standard transformer spec sheet. I wonder if the two secondaries are different for the pre-amp circuit and the valve heaters? I'm very much at the mercy of you guys as I've no tech knowledge. However, I'd suspect it is custom which would account for the stock replacement burning out. Briefly spoke to someone in the UK office and I've fired off those pics to them but I suspect it'll not have the important info that they'd need to identify it. Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 14, 2022 Share Posted November 14, 2022 OoI what are the three valves? That might help work out what spec transformer is needed. IIRC they are not all the same. Also is it just my eyes or is there a nut missing from the pre-amp board mountings - top right? Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted November 14, 2022 Share Posted November 14, 2022 1 hour ago, TimR said: 0.8amps at 12V is tiny. Stick it into any amp repair shop and they'll fix your issue and fit a replacement. 9.6 VA (Watts) must be preamp. I think you're overthinking this. A transformer is a transformer. Basic component. You could even replace it with two separate ones if there's space and it's cheaper. 12v is heater, and then there's the preamp which could be running anywhere from 9v to 200v+ - wouldn't you need to know that to spec a transformer? 1 Quote Link to comment Share on other sites More sharing options...
TimR Posted November 14, 2022 Share Posted November 14, 2022 5 hours ago, LukeFRC said: You could even replace it with two separate ones if there's space and it's cheaper. 12v is heater, and then there's the preamp which could be running anywhere from 9v to 200v+ - wouldn't you need to know that to spec a transformer? Yes. But if you took it to a transformer builder they could disassemble it, count the windings and build a new one. They're not mystical objects. It doesn't look like a very big transformer. What's the amp rated at? Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 14, 2022 Share Posted November 14, 2022 The amp rating is moot, the transformer only powers the pre-amp tubes. I agree that the only reason it would blow is if there's something downstream is drawing a lot more current than it should be. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 11 minutes ago, TimR said: It doesn't look like a very big transformer. What's the amp rated at? 2 x 500 watts 4 ohms / 1 x 1000 watts 8 ohms bridged... confusing labelling on the amp itself as it says 2/4 ohms but never run bridged and never below 4 ohms. Bear in mind the power section is class D and transformer is just for preamp valves. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 14, 2022 Author Share Posted November 14, 2022 Just now, Bill Fitzmaurice said: The amp rating is moot, the transformer only powers the pre-amp tubes. I agree that the only reason it would blow is if there's something downstream is drawing a lot more current than it should be. I alluded to that earlier but don't have enough tech education to know how that works. Could it be that the power module is too big for the front end to power... am I simplifying the language? Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted November 14, 2022 Share Posted November 14, 2022 1 minute ago, warwickhunt said: I alluded to that earlier but don't have enough tech education to know how that works. Could it be that the power module is too big for the front end to power... am I simplifying the language? I would imagine the pre and digimod are completely separate circuits. Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 15, 2022 Share Posted November 15, 2022 10 hours ago, LukeFRC said: I would imagine the pre and digimod are completely separate circuits. They are. The unit top right in the photo is the power amp and is totally self-contained. Everything else in the case is for the pre-amp valves and controls. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 15, 2022 Author Share Posted November 15, 2022 13 minutes ago, BigRedX said: They are. The unit top right in the photo is the power amp and is totally self-contained. Everything else in the case is for the pre-amp valves and controls. In layman's terms can anything in the power section/output affect what happens before it? Could the output / power section be the cause of the transformer burn out? Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted November 15, 2022 Share Posted November 15, 2022 1 minute ago, warwickhunt said: In layman's terms can anything in the power section/output affect what happens before it? Could the output / power section be the cause of the transformer burn out? Unlikely Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 15, 2022 Author Share Posted November 15, 2022 Dang! Transformer is no longer in production but I was forwarded this... 1 Quote Link to comment Share on other sites More sharing options...
BigRedX Posted November 15, 2022 Share Posted November 15, 2022 That's interesting. Can you follow where the different wires go in the amp - especially those connected to the mains side? Quote Link to comment Share on other sites More sharing options...
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