warwickhunt Posted March 5, 2023 Author Share Posted March 5, 2023 5 minutes ago, BassmanPaul said: I can't remember if you contacted the manufacturer if not that's who I'd be screaming at!! If you did I'd still be screaming at them! Yes I contacted the manufacturer but they've changed ownership/name 3 times and the amp is 18 years old. I managed to contact the company who made the transformer and it was a custom make. I have a gut feeling that as the last replacement transformer lasted hours and had no visible damage (but was dead) and this replacement is EXACTLY the same that there is an inherent issue somewhere else. Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 I agree. Do you at least have the proper schematic? Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 Looking again at the photo you posted, if all else fails I think you could fit a non toroid transformer possibly one from Hammond. That said you have to discover if the tube section has a problem or if the transformer it self design is faulty. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 5, 2023 Author Share Posted March 5, 2023 1 minute ago, BassmanPaul said: Looking again at the photo you posted, if all else fails I think you could fit a non toroid transformer possibly one from Hammond. That said you have to discover if the tube section has a problem or if the transformer it self design is faulty. Yes, I need to know what burnt out the first transformer (it was 18 years old), that subsequently killed the next 2 brand new transformers. The repair guy fitted a thermal trip and a fuse, however the trans didn't overheat or trip the fuse. Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 (edited) What are the tubes that the mp uses? What size fuse did he install? I must admit I'd love to get my hands on your amp! My curiosity is surging!! LOL Edited March 5, 2023 by BassmanPaul Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 5, 2023 Author Share Posted March 5, 2023 3 minutes ago, BassmanPaul said: What size fuse did he install? I must admit I'd love to get my hands on your amp! My curiosity is surging!! LOL I'll check on fuse size. Just plain odd that the previous trans lasted 3 hours at bedroom volume (not continuous) and had no visible damage (unlike the first) but tested 'dead' and this one has no visible damage... as yet untested. One daft thought is that I have no means of testing that this fuse is OK other than OK visually; one should never assume! Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 You can pick up a multimeter very cheaply that would be adequate for such simple tests. it could be that the fuse has blown which is why the tube section doesn't work. 1 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 5, 2023 Author Share Posted March 5, 2023 (edited) 26 minutes ago, BassmanPaul said: You can pick up a multimeter very cheaply that would be adequate for such simple tests. it could be that the fuse has blown which is why the tube section doesn't work. On my 'to do' list for tomorrow. Be here tomorrow from Amazon Edited March 5, 2023 by warwickhunt 2 Quote Link to comment Share on other sites More sharing options...
3below Posted March 5, 2023 Share Posted March 5, 2023 I hope this as simple as a failed fuse. They sometimes fail for no explicable reason (or underlying fault) but this in my experience is very rare. 1 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 2 hours ago, warwickhunt said: On my 'to do' list for tomorrow. Be here tomorrow from Amazon Which one did you purchase? Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 5, 2023 Author Share Posted March 5, 2023 Just now, BassmanPaul said: Which one did you purchase? Basic https://www.amazon.co.uk/dp/B00TM0W8ZY?psc=1&smid=A3ROO57IJZEV22&ref_=chk_typ_imgToDp Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 5, 2023 Share Posted March 5, 2023 That should be fine for what you need. I told you they were cheap! 1 Quote Link to comment Share on other sites More sharing options...
agedhorse Posted March 5, 2023 Share Posted March 5, 2023 (edited) First of all, that thermal protection isn't going to do much because it's on the outside of all of the wrappers so it will be measuring quite a bit less temperature than what's really present on the coil. The coil can overheat without the core overheating on a small part like that. Is the coil really overheating? Only a proper forensic evaluation (called a transformer "necropsy") will determine the true cause of the fault. The fuse should be slow blow (or time lag) and sized at a minimum of 1.25x the rated continuous primary current. For a toroid, it's possible that the inrush current (which is higher than for an EI transformer) might require an adjustment of this multiplier from 1.25 to 1.5, but this needs to be done after verifying that the transformer is not overloaded. There must be enough primary turns for the core material to prevent magnetic saturation, this design parameter is voltage and frequency dependent. If the transformer saturates, the primary current will be higher as will be the heating effect. Now for the real stuff... do you know what the input current is to the power supply. It looks like a FWB input capacitor filter. The transformer needs to be designed around the derating factor for this particular power supply topology. For this configuration, the rated current of the transformer multiplied by .65 is the usable current for the circuit being powered. It's possible that somebody forgot this when designing the power supply. There's more to solving this problem than replacing a part, you need to know what the maximum current of the circuit is and work backwards with all of the necessary design and derating factors to be sure you have a viable solution. Edited March 6, 2023 by agedhorse 2 Quote Link to comment Share on other sites More sharing options...
BigRedX Posted March 6, 2023 Share Posted March 6, 2023 As the other owner of this amp, who never had any problems with the pre-amp section (mine were all with the completely separate power amp module going into protect mode when presented with dodgy mains supplies), I would suspect that a problem has developed with the pre-amp which is causing the transformer to blow, and if the protection circuit has performed properly the fuse to blow (does a visual inspection show it to be blown). I'm surprised that your tech hasn't been able to track down this underlying problem, because it is my understanding that the pre-amp is based on a simple "classic" design. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 @agedhorseI can't really comment on a lot of the 'tech' stuff you've kindly given insight on but to recap and give a bit of user insight. @BigRedX Power amp certainly never given me issue or gone into protect mode but I'll be getting the next tech to take that into account. @BassmanPaul Off to check the Valves/tubes type. Fuse - T250Ma I've ordered a multi-meter to do a test on the fuse as it looks intact but don't always trust that. Heat/Temp - Neither of the replacement transformers seemed to run hot or burn out. The recent replacement I tested the plate/casing directly above the transformer and it was barely warm, certainly as cool/cooler than any other amp that I own (Thunderfunk/EBS350HD/Bugera Veyron). The original transformer 'burned out' last year, it was genuinely toasted and burnt. The replacement should have been a direct drop in but it was a custom wind and not available, the tech who did the work took note of the amp requirements and the spec he could decode from the photos I supplied and ordered a higher spec transformer as the exact spec couldn't be matched. This ran in the house for about 3-5 hours (not continuous) then literally as I played it, it started to distort slightly, lose volume and then no output. The tech took this on the chin and ordered a new transformer, fitted the thermal and fuse. When he fitted this replacement, he did a quick test on the transformer he took out and it was simply dead but no visible damage or smell. The new transformer ran in the house on test, I then gigged it twice (3 hours each time) and then I set it up at home to do some recording and as I messed with my PC it literally went from working fine to having no output (power still operating cooling fan etc, no burning smell). As a footnote I have run signals both from the pre into a separate power (line out and effects send) and reverse I've gone from a differing pre into this power (effects return and line in); none of the in/out to this amp worked but I've no idea if that indicates a broader issue or if it would do that when the pre is dead Oh and just to be absolutely belt/braces I did a parallel test with another amp and they performed as expected (eliminating some vagary in the way I was testing). Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 @BassmanPaul I'm not sure if I need to whoop or groan! I whipped the valves (x3) out, as I knew they should be 12ax7 valves but I wanted to see if they were matching as the first one was blank and no brand. As I took them out I gave them a good examination and lo/behold as I drew out #3 it was discoloured reddish brown! I have no idea if this means it is dead but when my multimeter arrives, I'll run a test; Google seems to indicate pins 9 / 4&5 (correct me if wrong but I'll be testing all 3 the same way so should tell). Quote Link to comment Share on other sites More sharing options...
BigRedX Posted March 6, 2023 Share Posted March 6, 2023 Do you have the manual? I had a look when it used to be on the TecAmp website and I'm pretty sure that at least one of those valves should be different to the others. Regarding the Power Amp problems, it's a completely separate unit, so it shouldn't affect the pre-amp. What I found was that it was very susceptible to under-voltage issues. The Terrortones used to play a venue that had added a second stage in another part of the building and this would cause the power requirements to occasionally exceed what was available, at which point the amp would go silent and refuse to come back on. Every time it would be fine once I got it back home. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 4 minutes ago, BigRedX said: Do you have the manual? I had a look when it used to be on the TecAmp website and I'm pretty sure that at least one of those valves should be different to the others. Regarding the Power Amp problems, it's a completely separate unit, so it shouldn't affect the pre-amp. What I found was that it was very susceptible to under-voltage issues. The Terrortones used to play a venue that had added a second stage in another part of the building and this would cause the power requirements to occasionally exceed what was available, at which point the amp would go silent and refuse to come back on. Every time it would be fine once I got it back home. No manual or schematic sadly (despite me being the original owner), not sure about a different valve being required in 1 position? Power amp - Ah OK never had that problem but worth knowing. Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted March 6, 2023 Share Posted March 6, 2023 16 hours ago, 3below said: I hope this as simple as a failed fuse. They sometimes fail for no explicable reason (or underlying fault) but this in my experience is very rare. Fuses do age. Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted March 6, 2023 Share Posted March 6, 2023 you used to have a PDF of a manual ... do share, my other half is a fluent German speaker... Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 Just now, LukeFRC said: you used to have a PDF of a manual ... do share, my other half is a fluent German speaker... Doh... need to see if I can drag out my old PC (didn't bin it when I went to lap top) and find the file! Quote Link to comment Share on other sites More sharing options...
3below Posted March 6, 2023 Share Posted March 6, 2023 Obviously you can't check the the valves fully with a multimeter but there are some simple checks which might be informative (or not). Between Pins 4 - 9 & 5 - 9 you should get some resistance, I have never measured one but from some googling I get figures of 20, 16 or 6 Ohms. If your meter shows 0 or continuity there is a heater problem. More likely is that the meter will show 1 (i.e. no circuit continuity) which means the heaters have faulted and then melted. This could be one cause of transformer failure. Between pins 6 -8 and 1 - 3 the data sheets suggest you should get about (Anode resistance) 62.5 kΩ I would also measure 1 - 9, 2 - 9, 3 - 9 and 6 - 9, 7 -9, 8 - 9 If you get a 0 Ohms connection there is a fault in the valve that may have taken the transformer out with it. None of the above will give definitive answers but may provide pointers to what to investigate next. 1 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 I was using this as a very basic guide to see if it is dead (3 minutes in). Quote Link to comment Share on other sites More sharing options...
3below Posted March 6, 2023 Share Posted March 6, 2023 (edited) I took the hard way, I had not thought of looking on YouTube, showing my age and 'old' Physicist approach. Edited March 6, 2023 by 3below 1 1 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted March 6, 2023 Author Share Posted March 6, 2023 I'm only going to test the valves for basic operation to eliminate them + test the T250Ma fuse is OK (don't trust visual). As a side note - the tech who has done the work and fitted the new transformer(s), heat trip and fuse, would like the amp back (no further charges to me) as he won't be beaten on this and wants me to be fully satisfied. Quote Link to comment Share on other sites More sharing options...
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