midnightsizzler Posted May 12, 2008 Share Posted May 12, 2008 hi all, it's taken a new speaker, hammond 125dse, a new set of jj's and removal of the DSP (plus a few valve junior type tweakages) but at last I've got my valve special sounding really good, bright and sparkly with lots of bottom end and with EQ that actually works! I'm pretty stoked with the sound actually and probably won't change much more, except that it has a bit of a buzz I'm not sure how to go about fixing. It also has a bit of hum which I guess is because the heaters are AC wired, the hum isn't really a problem, and even the buzz isnt that bad either unless the volime is cranked but I'd be keen to get rid of it if possible. I bypassed the DSP with a wire from the treble pot wiper to volume pot outer lug and the wire wasn't shielded and is about 10" long so that could be the cause of the buzz but I'm only guessing? the only other thing I thought of was to replace the first filter cap with a 100uf, I'm using a 47uf now but it didn't seem to make any difference to the buzz. If anyone could offer any suggestions on how I might remedy this I'd be hugely grateful as I'm not too sure what could be causing it, thanks. Link to comment Share on other sites More sharing options...
layboomo Posted May 12, 2008 Share Posted May 12, 2008 Yup that 10" non-shielded wire could be the problem for sure.....as for the AC heaters if you have the wires twisted together tightly it shouldn't be a problem.....if they are pcb traces try twisted wire instead. If you replace the 10" wire with shielded cable you only want to ground the shield on one end. Good Luck! Link to comment Share on other sites More sharing options...
ricach Posted May 12, 2008 Share Posted May 12, 2008 I have the Valve Standard, and I didn't use a shielded wire to bypass the DSP and I have no hum problems. Its about a 10" run as as well, but I messed with the routing of the wire and taped it in place in order to eliminate any hum. Try moving/rerouting your jumper wire around. Link to comment Share on other sites More sharing options...
layboomo Posted May 12, 2008 Share Posted May 12, 2008 I have the Valve Standard' date=' and I didn't use a shielded wire to bypass the DSP and I have no hum problems. Its about a 10" run as as well, but I messed with the routing of the wire and taped it in place in order to eliminate any hum. Try moving/rerouting your jumper wire around. [/quote'] +1 also a solution.....wire routing can be really touchy sometimes...I had a marshall 50 watter that if the wire on the presence control wasn't in just the right spot it was nasty! Link to comment Share on other sites More sharing options...
midnightsizzler Posted May 12, 2008 Author Share Posted May 12, 2008 Yeah thanks I think you guys have nailed the problem re the buzz, I put a slightly longer piece of wire connecting the treble and master volume pots and found moving it around made the buzz go from virtually inaudible to quite bad. Unfortunately I now have a bigger problem now which has been plaguing me during these mods: something has failed somewhere and theres no sound only crackle. Last night I found the the DSP indicator LED had broken its solder joints and once that was resoldered it worked perfectly but an hour later the amp fizzed out in the same way it had stopped working during mods (which i attributed to several bad pots as changing them fixed it but i'd probably just moved it and made a good enough contact on the LED during reinstallation). I've tested all the pots and all seem good, everything was working perfectly before apart from the aforementioned buzz, all I can think is it may be the LED as it must still be in the circuit somehow, perhaps the non-attenuated signal has fried it, i guess it doesnt need to be there anymore anyway as the DSP is gone for good but haven't quite sussed how to remove the LED and switch from the circuit. I've checked the obvious stuff but am not sure what to check now, if anyone has any idea what may be causing this i'd appreciate any input, thanks Link to comment Share on other sites More sharing options...
midnightsizzler Posted May 13, 2008 Author Share Posted May 13, 2008 oops looks like the problem might have been a dodgy gain pot, it tested ok out of the amp but when replaced with a fresh one, the amp began working as before, although now theres sound the buzz is still there, even with shielded wire, it does get worse when the wires moved, it may just require some more clever re-routing than i've done so I'll experiment with that. Link to comment Share on other sites More sharing options...
layboomo Posted May 13, 2008 Share Posted May 13, 2008 oops looks like the problem might have been a dodgy gain pot' date=' it tested ok out of the amp but when replaced with a fresh one, the amp began working as before, although now theres sound the buzz is still there, even with shielded wire, it does get worse when the wires moved, it may just require some more clever re-routing than i've done so I'll experiment with that.[/quote'] Forgive me if you already know this but some people find out the hard way.... Before you solder a connection to a pot you should always turn it all the way down. If you leave it turned up you can overheat it and cause a drop out or "bad spot" on the control. Link to comment Share on other sites More sharing options...
midnightsizzler Posted May 13, 2008 Author Share Posted May 13, 2008 Thanks for the tip, Layboomo... no I did not actually know that, that probably explains why i've had to replace several pots during this project, us noobs don't know these things! Link to comment Share on other sites More sharing options...
midnightsizzler Posted May 18, 2008 Author Share Posted May 18, 2008 Forgive me if you already know this but some people find out the hard way.... Before you solder a connection to a pot you should always turn it all the way down. If you leave it turned up you can overheat it and cause a drop out or "bad spot" on the control. I think this might have caused the failure of several pots as i ran the jumper from treble wiper lug to outer volume pot lug, and probably didn't have them turned down when soldering, thus also possibly damaging the replacement ones. I've replaced the pots and made the jumper come off the trace behind the pot (rather than the pot itself to avoid overheating) and had the amp sounding great, even for the most part taking care of the buzz that was troubling me before. The problem now is that the sound always craps out, almost immediately or soon after just making a crackling noise and the faintest of guitar sound comes through with gain and volume on full but more crackle. Replacing the treble pot seems to fix this and makes it sound mint again but it always fails again quickly. I've gone over and over it and am reasonably sure there are no bad connections, but I'm at a loss to understand what could be causing the problem, unless another pot besides the treble is bad, (the volume and gain pot appear to be fine). I also now need to order pots from overseas as the only local place that had them doesn't stock them anymore, but first was hoping someone may be able to suggest what to check as I've drawn a blank! Thanks Link to comment Share on other sites More sharing options...
ricach Posted May 19, 2008 Share Posted May 19, 2008 On my valve standard, and I'm certain you'll find it on the special, I found the tab on the circuit board where the xformer plugs into is pretty wobbly and makes and breaks power to the circuitry. I soldered a jumper wire from the tab to the diode where the trace goes. This way I have a direct connect from xformer to diode. do this for both tabs. This might not be a problem for you now, but it will eventually. It can't hurt to eliminate it now. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.