Subthumper

Hi folks, bit of a puzzler this. I have a warwick rockbass with active pickups and eq. The battery is only lasting a month, however I have conducted a few tests and found that the barrel Jack is ok and that the connections are correct and that no current is flowing from.the battery when the bass is unplugged. What I have found though is that the current draw is 100mA which I think is rather high. Looking at the pickups they appear very similar to EMGs so going by their figures I'd be expecting about 1000 hours of playing time from the battery. I'm suspecting a fault in the actives and yet the bass sounds great, both pickups, one pickup, eq, no distortion, nice clean full sound and no noise. I have a bass with an EMG jazz pickup, and an MEC P pickup and the battery lasts years. Has anyone else experienced this or maybe know if this is normal behaviour? Any info welcome. Thanks for reading Cheers Just

Don't know how good they are but the Inmadout transformers from Italy are very reasonably priced. In particular they do do complete sets for the 100, 200 and 400 hiwatt amps, plus numerous fender marshall copies. Should hopefully be getting my hands on one soon so should be able to see what the quality is like. I built all my amps using recycled iron but in the future would prefer to use brand new as its impossible to know what's happened to a piece of kit over the years. Prices certainly get high once you pass the 100watt mark.

Give it a thump!! Bit crude but usually finds anything loose. Give everything a good wiggle whilst it's running. Hopefully it's just a service issue.

Is the wiring from the pickup a piece of mine I shielded coax or two normal thin bits of wire? If it's wire make sure it's twisted together, this will drastically reduce hum and Buzz. Don't forget also that any copper or paint shielding must be unearthed back to the Jack socket or other will cat like an antenna and make the problem worse. Earthing is a pain, I've seen it cause more arguments and problems than almost any other electrical/ electronic problem.

Slightly off topic but I've had many discussions with upright players who amplify their instrument about the best solution. Ive repaired numerous 2x10, 4x10 and 15 loaded cabs that have had their drivers turned inside out by over zealous use of a 500 watt amp and a double bass. I'm not an upright player myself but I think that there's definitely a market for a dedicated upright bass speaker cab. On the behemoth side of things then defo a 4x12 that really works.

Hmmm valves and surface mount components on the same PCB, it's just wrong in my book. Doesn't look like something that can be repaired, certainly not by your local amp tech like me.

Thanks guys and yes, I did mean RB.

Hi folks, does anyone know what the output specs are for the power amps in these? IE whether it's 300 + 100 watts RMS or peak? I've been asked to put a new transformer in one that has the American 115v transformer so need to find an appropriate replacement. Cheers Just

These did suffer from a weak transformer, I've replaced a few of these. The replacement that Ashdown supplied was a big bigger. It's not a big job for a tech to diagnose the where the fault lies, transformer, power supply or power amp. Get a tech to look it over and work from there. Ashdown are pretty good on the service front, worth telling them the serial number to gain some sympathy if it's the transformer.

I've not read the entire thread but spares and repairs can be obtained for these from MAJ electronic. I believe they bought up all the stock when HH closed the doors. I've worked on a few of these and they were very well made by today's standards. You don't see laced wiring on production stuff these days, just cable ties and hot glue gun glue.

[quote name='mikeydee' timestamp='1427479500' post='2730988'] Hi Bradwell, I repair amps all the time. So pre-amp is fine. Do any of the buttons on the front make any difference - esp mute if fitted. Next, do the valves light up (sorry) just asking. You've changed the valves already - Did you check the HT fuse ok? Check on a meter. Next: you can confirm power amp stage problem by seeing whether you get output by plugging guitar into return jack. If you get a strong signal, then the issue is probably send/return jacks - It's very common for low output to be caused by the send and return jacks oxidising. If output still low check the phase inverter (PI) valve. First is there any sign that the silver top has gone white? If so, then the glass has leaked. Better tho to replace the PI for another. If you don't have one, then take the one from V1 (nearest input jack) and then use your guitar via the return jack again. If it works then the PI was bad. If not, then you have not proven anything. At this point, you have to open the amp up to go any furthere and you need to know what you are doing in working with high voltage. There is a common problem of bias drift on TSL/DSL. This only effects certain serial numbers but can cause output TX to fail. Check the valve bases for signs of discolouration. They should be reddy brown but sometimes head black when this illness strikes. BTW I know everyone likes to rubbish cheap chinese parts but seriously Marshall will probably sell you the exact right TX for £30-50. They happily last 10-15 years. That's not too bad. Mike [/quote] +1 . The mains transformers all ways hum on the jcm 2000s. Worth also checking the 16 ohm output Jack. They use the switching earth tag to isolate the 4/8ohm outputs when the 16 ohm is used to prevent overloading the output transformer. The connector in the Jack sometimes gets dirty and makes a bad contact which can sound like a bad output valve or transformer. Give it a blast of switch cleaner and exercise it by pushing a Jack plug in and out a few times. As mentioned, going inside the amp involves high voltages, if your not sure what your doing take the amp to a tech. It really does hurt I promise!! One last thing. These amps are full of multi connectors which can all easily be mixed up. Photograph from all angles and Mark every single one before taking anything to bits . Good luck cheers Just

Wrap them in industrial cling film like the s stuff they use for pallet wrapping. Given especially good physical protection as well as keeping out damp and debris.

It's a fantastic cab and I'm totally impressed with it. I'm just trying to determine if I'm pushing it too far or if I have an amp or valve problem. I have access to a 1kw 8x10 so I'm going to see how far I can push the amp before meltdown. Looking like two cabs will be the answer...how awful.

Is that 2x12 sealed or ported?

It's £32 + p&p from Wyse.

[quote name='Bottle' timestamp='1425937954' post='2712608'] I'd like the bassman clone. I think that'd sound awesome. Just did a quick search on Amazon and the book is unavailable at the moment - all the second-hand copies are £50-ish and up Try contacting Vyse amps ,that's who do all the Torres amp kits. [/quote]

I did the torres thunder bass. Great amp, pretty much a bassman. The pre section is identical to the mesa bass 400 minus the graphic. Good fun to build though it does need a few skills and the best bit is it sounds great. Well worth getting a copy of inside tube amps by Dan Torres, probably the best £30 I've spent on knowledge. Good explanations and nice easy to understand drawings and charts. I think they offer a 200 watt version now as well as the 120watt.

It's the old compact 15.

As the title suggests really, it's what I'm using and was wondering if anyone's got the amp to push the driver to its limits? I know it's rated at 450 watts but it's frequency and sheer grunt and im wondering if the amp is pushing the cone too far. Anyone else had a similar experience?

No or not that I know of. It takes a lot of energy to reproduce bass frequencies and too small a transformer will result in saturation, which is where the iron core has absorbed as much electromagnetic energy as it can and then starts to distort and lose frequency response. Sometimes this is good thing on guitar amps as is forms part that amps distinct tone. In the early days guitar amps deliberately had small output transformers to limit the low end to preserve the frail speakers. I recently worked on a a couple of peavey 5150/6505 60 watt combos. One was an American one the other was a Chinese one. The output transformer of the Chinese one is about half the size and difference in sound is huge. The U.S. one sounds big and articulate and the Chinese one is rather thin and strangled sounding. Hence this is why all the best sounding valve bass have huge heavy transformers. There is some news on lightweight valves though. Korg have just announced their NUTUBE which is a miniature pre amp valve. Check it out.

Some fantastic German techie words in there. Nearly ordered one by mistake when I thought I was on the translation icon. Not cheap though.

Yes, that was on the tubepath heads. Ampeg did a similar thing with the SVT3 except it was a valve driving the mosfet power stage and the valve had an adjustable plate voltage to introduce some form of compression/grit/drive type thing.

That style of thing is a lot easier to do than squeezing things into a 2U rack. It uses standard transformers rather than custom made ones. And no fan. Should I make one? If so what do folks want to see feature wise?

It's well worth researching the speakers as you may be surprised at their value if they're working. The columns if in good condition are becoming collectable so best bet is sell them and get something you want that will do the job.

I've worked on quite a few ampegs and they all had solder issues. Every one I get I completely strip down and resolder anything that looks remotely like it could give a problem. Running in the workshop is not the same as a gig, especially regarding heat and vibration. Some faults like this can be a pig to find so I'm sure your techie did all the right things. I've just had a,week myself of amps that refuse to be fixed so I feel their and your pain. Worth getting some the American forums too, just Google your amp and its fault and any threads will come up. Whatever stuff you find out or print up will be appreciated by your techie. Good luck. Cheers Just