Bombacaototal wrote: ↑Tue Jan 28, 2020 3:04 pm
Marcus, it is very easy to drop it in. The Mayer topology is essentially the 004 minis filters, and some different LNFBs and values. So it makes sense having the filters in this circuit.
I tried my 002 and 004 filters with the inductor bypassed and it works fine. I preferred the sound with the inductor just because I felt it tightened the bottom nicely
I’ve done them connected to one another like Dumble but also used the terminal strip in 2 other occasions. The terminals made it easier for me but going straight looks nicer
thanks, where did you get your switches etc? I hope it was tube town as I'll need to get a new face plate made by them I wonder if I should add a FET boost...that means relays and power boards if I want it on a footswitch...hmm maybe not then.
The switches were from mouser. I can check the part number when I am home. I do like the FET but have no relay on my amp as space was a real constraint
I put the amp on again and noticed if I was touching the handle and the mains switch the hum disappeared , so i got my meter out and I'm getting 4v AC between the handle and the chassis crews???? I obviously have some sort of grounding issue, I'll pull it form the cab again. I also noticed when I touched one of the reverb leads the nasty noise came back so I need to look at that.
Hi Marcus, looks like the problem is already sorted! Really, cold solder joints (on the heaters) can lead to very strange problems. Had the same sort of thing on a recent build.
I'm not surprised at all by the blue flashing in the tubes. Sounds like you had the amp turned up pretty high when you saw that. I noticed similar behaviour in my Marshall 50 and 100W clones. Blue glow is normal due to (ionised I believe) stray gasses and they light up more when more current passes through the tube/vacuum. That's at least my observation. To make sure it is what I think it (harmless) you could upload a short video of it.
right then, it seems that one of the long chassis bolts was picking up AC current from the rectifier board that is very close. There's a good 5-10mm of clearance between any conductive parts but it seems that's what's happening with the hum???? weird. I've removed the bolt and the amp is quiet again.
Any suggestions apart from moving the rectifier board??
@Rootz, the blue flashing coincided with the horrible noise i was getting. it might have been the reverb connections vibrating possibly as Xtain mentioned.
At least I have a nice new boiler in the house now and warmth
norburybrook wrote: ↑Tue Jan 28, 2020 4:29 pm
right then, it seems that one of the long chassis bolts was picking up AC current from the rectifier board that is very close. There's a good 5-10mm of clearance between any conductive parts but it seems that's what's happening with the hum???? weird. I've removed the bolt and the amp is quiet again.
Any suggestions apart from moving the rectifier board??
@Rootz, the blue flashing coincided with the horrible noise i was getting. it might have been the reverb connections vibrating possibly as Xtain mentioned.
At least I have a nice new boiler in the house now and warmth
M
Hi Marcus. I know you don't want to move things but regarding the rectifier board being close to the chassis bolts this is one of the reasons I use all stand up transformers these days. I use to hate giving up 3-4 in of chassis real estate for the power transformer. I find it easier to work as well when things aren't so tight. Pic of a stand up transformer build with power supply and rectifier on one board and room to spare.
Congrats on your new boiler!
20200127_111642.jpg
Cheers
Guy
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Martin, thanks it's a 500v cap too and that was the highest I could find , but yes it's on it's limit. Now I've removed the chassis bolt and replaced the phono socket on one of the reverb cables the amp has been perfect again all afternoon, no problems at all.
Guy, yes I hear you , however the rectifier board is on the side of the chassis vertically so it wouldn''t help, the transformers on this build are both stand up by the way
I'll move the board along at some other time to mount it further away from that long bolt. On these chassis they use cage nuts and long fender type bolts to the bottom of the chassis.
norburybrook wrote: ↑Wed Jan 29, 2020 8:44 am
Martin, thanks it's a 500v cap too and that was the highest I could find , but yes it's on it's limit. Now I've removed the chassis bolt and replaced the phono socket on one of the reverb cables the amp has been perfect again all afternoon, no problems at all.
Seems unlikely that a small signal issue would be the cause of the arcing you saw. Intermittent faults are the worst...
norburybrook wrote: ↑Wed Jan 29, 2020 8:44 am
Martin, thanks it's a 500v cap too and that was the highest I could find , but yes it's on it's limit. Now I've removed the chassis bolt and replaced the phono socket on one of the reverb cables the amp has been perfect again all afternoon, no problems at all.
Seems unlikely that a small signal issue would be the cause of the arcing you saw. Intermittent faults are the worst...
unless the arcing i saw was just regular blue tube light but caused by the loud crackle the reverb cable was causing when the dimed amp was vibrating it?
Have you considered a nylon bolt and nylon nut? That might be a better solution then no bolt at all?
With respect, 10thtx
that's a very good suggestion I'm sure in the long run I'll just move the board. It's only 2 holes to drill. I don't use this amp much so it's not a pressing issue. It's a lovely amp but you'd need pedals for OD and I tend not to use OD pedals much these days. In the studio the Princeton reverb has a lovely clean recorded tone, so i think of the JM amp as a loud live amp
I wonder if I should add a FET boost...that means relays and power boards if I want it on a footswitch...hmm maybe not then.
Heater wire ends touching the chassis? Had that once too. Gives that intermittence too.
