Search found 2709 matches
- Thu May 16, 2024 1:44 pm
- Forum: Fender Discussion
- Topic: 1976 Fender Vibrolux refresh help
- Replies: 8
- Views: 159
Re: 1976 Fender Vibrolux refresh help
Should I leave the thermal fuse and ground changes as is or remove them? 'Ground changes'? You mentioned that the ground pin had been removed from the mains plug. That certainly needs sorting, eg fit a new plug. Replacing the mains cable might be more difficult, as a big bertha iron might be needed...
- Tue May 14, 2024 11:47 pm
- Forum: Technical Discussion
- Topic: Modded Tremolux
- Replies: 39
- Views: 8202
Re: Modded Tremolux
I guess their definition of surge voltage capability may end up being more arduous than your amp subjects them to?johnnyreece wrote: ↑Tue May 14, 2024 6:16 pm ... According to the manufacturer, these are 450VDC working; 500VDC surge. ...
- Mon May 13, 2024 12:39 pm
- Forum: Technical Discussion
- Topic: Modded Tremolux
- Replies: 39
- Views: 8202
Re: Modded Tremolux
... My electrolytics are rated for 450V, but with a 5U4, my B+ nears 500V while warming up. Is this okay, or should I get higher rated caps? Their short term surge voltage rating might be up to 20% above their max working voltage rating. So as the near 500V will only last for 20 seconds or so, a ti...
- Sat May 11, 2024 4:31 pm
- Forum: FAQs
- Topic: Tube amp grounding article/info/links
- Replies: 26
- Views: 80705
Re: Tube amp grounding article/info/links
I have read multiple times on this forum and other forums that the preamp should be grounded at the input jack. I have posted about this previously. I am the outlier here. I never ground at the input jack, yet, I get good results. I was taught by someone (online) who I respected, to run a buss from...
- Sat May 04, 2024 9:59 pm
- Forum: Technical Discussion
- Topic: JTM45 Build, looks alive but no sound,
- Replies: 7
- Views: 267
Re: JTM45 Build, looks alive but no sound,
V1B cathode voltage of 5.5V is bad.
- Wed May 01, 2024 6:39 pm
- Forum: Technical Discussion
- Topic: Fender question
- Replies: 10
- Views: 296
Re: Fender question
As I recall, Fender were making valve amps with pcb mounted pots from the early 80s.
- Sat Apr 27, 2024 4:27 pm
- Forum: Technical Discussion
- Topic: Add an HT Fuse?
- Replies: 10
- Views: 626
Re: Add an HT Fuse?
Especially if there's a valve rectifier, I prefer to add a HT fuse in the CT return to 0V common of the HT winding. That seems to be more common in early 60s amps, such as JTM45 or AC50 https://el34world.com/charts/Schematics/files/Vox/Vox_ac50.pdf In this arrangement, F500mA works fine with my JTM4...
- Fri Apr 26, 2024 1:03 pm
- Forum: Technical Discussion
- Topic: Panel/Faceplate Engravers in the UK?
- Replies: 3
- Views: 312
Re: Panel/Faceplate Engravers in the UK?
Yes, Michael does great work, and very reasonably priced.
I just sent him a photo of a sketch with dimensions, but Im sure he can work with CAD files.
I just sent him a photo of a sketch with dimensions, but Im sure he can work with CAD files.
- Wed Apr 24, 2024 5:37 pm
- Forum: Marshall Discussion
- Topic: 2024 Monkeymatic Fiddy 1987
- Replies: 2
- Views: 745
Re: 2024 Monkeymatic Fiddy 1987
I'm not keen on the OT being so close to the input stages. A screening plate can help to keep things stable in that type of scenario so perhaps think about how one might be squeezed in before everything is set in stone.
- Sun Apr 21, 2024 5:00 pm
- Forum: Technical Discussion
- Topic: '63 Selmer Treble n bass dilemma..
- Replies: 4
- Views: 393
Re: '63 Selmer Treble n bass dilemma..
do these amps draw more current than a jtm45? I think so, due to the much lower impedance OT, but then so does a JTM50, yet the same spec mains transformer got used, for the early production at least (as I understand it). As I recall, the T&B mains transformer was a bit smaller than a JTM45 type. P...
- Sun Apr 21, 2024 8:24 am
- Forum: Technical Discussion
- Topic: '63 Selmer Treble n bass dilemma..
- Replies: 4
- Views: 393
Re: '63 Selmer Treble n bass dilemma..
If you send the duff mains transformer to Luke at Transformer Equipment, I think he could backwards engineer it and build a clone, for a fraction of the MM price. But yes, a good JTM45/50 mains transformer should be electrically fairly similar. A friend has a dead T&B MkII that needs a lot of work, ...
- Fri Apr 19, 2024 10:37 am
- Forum: Technical Discussion
- Topic: Taming amp gain in single channel deluxe reverb build
- Replies: 52
- Views: 1846
Re: Taming amp gain in single channel deluxe reverb build
... So the 47k would then be a voltage divider with the plate resistance(tube and resistor)? That's exactly it! The Thevenin equivalent circuit for the triode stage is a voltage source (zero impedance) in series with about a 40k resistance (anode load resistor // valve's internal anode resistance)....
- Fri Apr 19, 2024 10:31 am
- Forum: Marshall Discussion
- Topic: Bad case of ghosting...I've tried everything.
- Replies: 5
- Views: 630
Re: Bad case of ghosting...I've tried everything.
I suggest cleaning up all connections to the chassis. One or more of those lugs etc may have developed corrosion etc, preventing a good connection.
- Thu Apr 18, 2024 5:19 pm
- Forum: Technical Discussion
- Topic: Taming amp gain in single channel deluxe reverb build
- Replies: 52
- Views: 1846
Re: Taming amp gain in single channel deluxe reverb build
... I biased the 6V6 to around 415V and 20mA, so basically 20mV of current ... TP 37 and 38 206V AC TP39 11.4 So your HT voltage is higher than the Fender schematic you're referencing. I guess the Z HT node voltage will be higher too. More voltage on the screen grids means a higher stage gain for t...
- Thu Apr 18, 2024 8:55 am
- Forum: Technical Discussion
- Topic: Taming amp gain in single channel deluxe reverb build
- Replies: 52
- Views: 1846
Re: Taming amp gain in single channel deluxe reverb build
I just finished the initial build of a single channel deluxe reverb, sans tremolo. I'm using a classictone 40-18019 PT and the OT from a Hammond AO35. The hammond has 2 EL84's into an 8r load. I figured the 6V6 would be relatively close. ... There seems to be some confusion as to whether you've use...