highwayone Posted June 13, 2016 Share Posted June 13, 2016 (edited) HELP!!!!! My amp lost power at a gig last week and I took it for a repair and he said the fuse had gone and that there may be an underlying issue. He changed the fuse and I have used it at practise tonight and it has f@@ked up again. The power is still there (maybe because he put a higher rated fuse in) but the sound faded in and out and then went altogether. The repair guy put it on an oscillator reader thingy and there is usually a thin wavy line but mine was very thick and he said he had never saw (although he usually repairs older style valve amps and these are very flimsy Chinese manufacturing by the looks of it). Anybody on here got any ideas or know anyone Leicester way that could help?? Thanks. Just got back and one of speakers was rattling (abm210t) and this was inside [URL=http://s438.photobucket.com/user/karlosfandango1/media/Mobile%20Uploads/2016-06/20160613_210842_zps9t3ujwrl.jpg.html][IMG]http://i438.photobucket.com/albums/qq104/karlosfandango1/Mobile%20Uploads/2016-06/20160613_210842_zps9t3ujwrl.jpg[/IMG][/URL] [URL=http://s438.photobucket.com/user/karlosfandango1/media/Mobile%20Uploads/2016-06/20160613_210831_zpswttgjzfd.jpg.html][IMG]http://i438.photobucket.com/albums/qq104/karlosfandango1/Mobile%20Uploads/2016-06/20160613_210831_zpswttgjzfd.jpg[/IMG][/URL] [URL=http://s438.photobucket.com/user/karlosfandango1/media/Mobile%20Uploads/2016-06/20160613_210946_zpsvkvvjthr.jpg.html][IMG]http://i438.photobucket.com/albums/qq104/karlosfandango1/Mobile%20Uploads/2016-06/20160613_210946_zpsvkvvjthr.jpg[/IMG][/URL] Could this have anything to do with it? Got 2 gigs at the weekend so any help would be appreciated. Thanks. Edited June 14, 2016 by highwayone Quote Link to comment Share on other sites More sharing options...
Bigwan Posted June 14, 2016 Share Posted June 14, 2016 (edited) Have you got another cab you can try with the amp? A goosed crossover will certainly be an issue for an amp (depending on the manner in which it is goosed of course!). Edited June 14, 2016 by Bigwan Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 14, 2016 Share Posted June 14, 2016 This is possibly the crossover, as that resistor should be on the board. Just so happens I have a working crossover over for that cab you may have for Free! Minus the postage costs. Although if you can live without the tweeter just take the cross over circuit out and don't wire the tweeter up but keep it in place. The bass man 500 is the one with the valve pre amp and class d power section from the Rumble 500. I would check the fuses and try with another cab. If it works it's the cross over from your cab. Replace or repair (as said I have one you may have) possible that it's just the resistor failure. If the amp doesn't work with another cab then check the valve(s). Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 14, 2016 Author Share Posted June 14, 2016 It was connected up to two cabs when it happened, both abm210t. Would this issue with the crossover still have happened? Thanks. Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 14, 2016 Share Posted June 14, 2016 (edited) [quote name='highwayone' timestamp='1465893781' post='3071834'] It was connected up to two cabs when it happened, both abm210t. Would this issue with the crossover still have happened? Thanks. [/quote] I'm not an expert in this area but possibly if a crossover malfunction happened, which it looks like it did badly (resistor dropped out!) then it's possible that could of effected how the amp sees the load etc and made it shut down or possibly cause other issues. Despite another cab being attached. This would be my theory since there is evidence of that. Have you tried the amp with another cab or the one with the working crossover? Too add those abm cabs are not put together well. There not glued enough and there build design and quality is just a bit poor. The mag series are seemingly put together much better but with lesser quality materials, but they are stronger cabs. I've had a few abm cabs and seeing your inner pics brought it all back. The fact a resistor dropped out is also not a good sign. I have a mag cab currently it's not as light and arguably doesn't sound as good but it's solid. I'm not an Ashdown hater but the abm cabs should be better. And while I'm having a rant the power section of the abm amp series (up until the new class d evo 4) is of bad design too! They sound good but the design makes them prone to fail. Anyhow let us know if the head works with another cab. Likely it's ok. Check the old guy hasn't put wrong fuses in. No matter what they should be of the correct rating! Edited June 14, 2016 by Twincam Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 14, 2016 Author Share Posted June 14, 2016 No I haven't. The amp went off at rehearsal last night and I assumed it wouldn't 'fire' up again . Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 14, 2016 Share Posted June 14, 2016 [quote name='highwayone' timestamp='1465896891' post='3071872'] No I haven't. The amp went off at rehearsal last night and I assumed it wouldn't 'fire' up again . [/quote] Well let us know the score with another cab. Check the fuses are good and the right ratings first. Quote Link to comment Share on other sites More sharing options...
luckydog Posted June 14, 2016 Share Posted June 14, 2016 The component that fell from the crossover was the series resistor limiting power to the hf unit. The 'thick' wavy line on the 'scope could well be due to high frequency oscillation, perhaps too high to hear even, and that fits with damage to that resistor and the amp lacking power/shutting down/blowing fuses. Seems there is a fault in the amp causing it to oscillate at high frequency. With these clues, a competent technician should be able to readily trace and fix it. However, it's not really a DIY repair, and the fault is likely to be deep within the electronics of the amp, and is perhaps an interaction with those speakers. In the meantime, hooking it up to different speakers risks damaging them, so that seems a bad idea. Best to take the amp and the speakers that demonstrate the problem in for repair. HTH ! LD Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 14, 2016 Share Posted June 14, 2016 [quote name='luckydog' timestamp='1465897588' post='3071883'] The component that fell from the crossover was the series resistor limiting power to the hf unit. The 'thick' wavy line on the 'scope could well be due to high frequency oscillation, perhaps too high to hear even, and that fits with damage to that resistor and the amp lacking power/shutting down/blowing fuses. Seems there is a fault in the amp causing it to oscillate at high frequency. With these clues, a competent technician should be able to readily trace and fix it. However, it's not really a DIY repair, and the fault is likely to be deep within the electronics of the amp, and is perhaps an interaction with those speakers. In the meantime, hooking it up to different speakers risks damaging them, so that seems a bad idea. Best to take the amp and the speakers that demonstrate the problem in for repair. HTH ! LD [/quote] I do agree. Although I would still be tempted to hook it up to a working cab at low volume to see what the crack is. If it's bad then power off right away and take it to a tech. Seems this guy you taken it too might not know that much about the more modern amps??? How old is the amp? these can't be that old. I thought they only realised it within the last few recent years. Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 14, 2016 Author Share Posted June 14, 2016 Think the amps only just over a year old but I picked it up 2nd hand. Thanks all for the help and advice Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 14, 2016 Author Share Posted June 14, 2016 [quote name='luckydog' timestamp='1465897588' post='3071883'] The component that fell from the crossover was the series resistor limiting power to the hf unit. The 'thick' wavy line on the 'scope could well be due to high frequency oscillation, perhaps too high to hear even, and that fits with damage to that resistor and the amp lacking power/shutting down/blowing fuses. Seems there is a fault in the amp causing it to oscillate at high frequency. With these clues, a competent technician should be able to readily trace and fix it. However, it's not really a DIY repair, and the fault is likely to be deep within the electronics of the amp, and is perhaps an interaction with those speakers. In the meantime, hooking it up to different speakers risks damaging them, so that seems a bad idea. Best to take the amp and the speakers that demonstrate the problem in for repair. HTH ! LD [/quote] Thanks for this info. I can pass it on to the repair guy. Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 15, 2016 Author Share Posted June 15, 2016 [quote name='Twincam' timestamp='1465890632' post='3071791'] This is possibly the crossover, as that resistor should be on the board. Just so happens I have a working crossover over for that cab you may have for Free! Minus the postage costs. Although if you can live without the tweeter just take the cross over circuit out and don't wire the tweeter up but keep it in place. The bass man 500 is the one with the valve pre amp and class d power section from the Rumble 500. I would check the fuses and try with another cab. If it works it's the cross over from your cab. Replace or repair (as said I have one you may have) possible that it's just the resistor failure. If the amp doesn't work with another cab then check the valve(s). [/quote] These cabs have a low/off/high switch on the back. Are these for the tweeter? Can I just switch them to off to bypass the resistors that have fell off? Thanks Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 15, 2016 Share Posted June 15, 2016 (edited) [quote name='highwayone' timestamp='1465985544' post='3072577'] These cabs have a low/off/high switch on the back. Are these for the tweeter? Can I just switch them to off to bypass the resistors that have fell off? Thanks [/quote] Yes it's for the tweeter. Not sure if it bypasses totally. I would think in the off position it would totally be off as the switch is making a simple connection. It's not a complex circuit. I would be tempted to try the amp at low volume level if it works at low level play it till the amp is warmed up then slowly raise the volume any odd noises turn off immediately. And make sure the tweeter position is off or try a good cab. However there could be a risk of further damage to the amp we just don't know. I'm stupid so I would give it a go before taking it to a tech. Let us know the outcome. Edited June 15, 2016 by Twincam Quote Link to comment Share on other sites More sharing options...
luckydog Posted June 15, 2016 Share Posted June 15, 2016 If the amp is unstable, it's really best not to feed it speakers to eat. Thing is, you might not even be able to hear the frequencies involved, being so high..... Just sayin'.......and you know the amp's got a fault here! LD Quote Link to comment Share on other sites More sharing options...
highwayone Posted June 15, 2016 Author Share Posted June 15, 2016 [quote name='luckydog' timestamp='1466024301' post='3072932'] If the amp is unstable, it's really best not to feed it speakers to eat. Thing is, you might not even be able to hear the frequencies involved, being so high..... Just sayin'.......and you know the amp's got a fault here! LD [/quote] Yeah taken the amp in for repair,don't think the cab tweeter has caused an issue. Look out for a fender amp for sale on here soon😁 Quote Link to comment Share on other sites More sharing options...
3below Posted June 15, 2016 Share Posted June 15, 2016 [quote name='highwayone' timestamp='1465849185' post='3071620'] ........... I took it for a repair and he said the fuse had gone and that there may be an underlying issue. He changed the fuse and I have used it at practise tonight and it has f@@ked up again. The power is still there (maybe because he put a higher rated fuse in) ......... [/quote] Replacing a fuse with a higher rated one does not inspire confidence in your repair person (unless a particular fusing issue is well known with the bassman 500 amp). My take is that there is an underlying problem, just needs the right person to find out what it is and rectify. Quote Link to comment Share on other sites More sharing options...
Bigwan Posted June 16, 2016 Share Posted June 16, 2016 +1. Stop visiting said repair person IMMEDIATELY!!! That's the oldest and potentially most damaging bodge in the book, second only to replacing the fuse with a nail or bit of foil! Now if the fuse SHOULD be failing to protect the rest of the amp it won't. Cue the magic smoke smell... Quote Link to comment Share on other sites More sharing options...
Merton Posted June 16, 2016 Share Posted June 16, 2016 [quote name='Twincam' timestamp='1465896351' post='3071866'] And while I'm having a rant the power section of the abm amp series (up until the new class d evo 4) is of bad design too! [/quote] Totally OT but the new EVO IV ABM is not class D, it's still Class A/B They have done some class D ABMs but they are all with the EVO III preamp as far as I know. Quote Link to comment Share on other sites More sharing options...
Twincam Posted June 16, 2016 Share Posted June 16, 2016 [quote name='Merton' timestamp='1466061729' post='3073050'] Totally OT but the new EVO IV ABM is not class D, it's still Class A/B They have done some class D ABMs but they are all with the EVO III preamp as far as I know. [/quote] Ah I thought they had all moved over. Well hopefully there not using the exact same power stage design just "updated" as the design from the first abm to the evo iii is terrible. Not in sound or power I may add. Just in reliability. I've had issues and I've seen others have very similar issues. Although plenty are still running fine. Put me off though. Quote Link to comment Share on other sites More sharing options...
zep bass Posted July 9, 2016 Share Posted July 9, 2016 Hi there, I've been through three Bassman 500 amps within a couple of months , all with the same problem. Was looking at getting something to give me that Svt grit with half the weight. Tried the heads with multiple cabs and still pop. Sent the first one back to fender same thing. They claimed first off that the wrong type of fuse was installed, then when it happened again they said it could be the voltage in the area, as they are based on 230 volts rather than 240 and that could be behind it. After the third head I just wanted my money back. Really disappointed, when it worked it sounded great. Was hoping the problem would go away. I think that there is a whole batch issue that fender have on that particular consignment or the design cannot cope with 240 volts and has a bad design in that area. Real shame.... Quote Link to comment Share on other sites More sharing options...
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