Search found 2703 matches
- Sat Apr 27, 2024 4:27 pm
- Forum: Technical Discussion
- Topic: Add an HT Fuse?
- Replies: 7
- Views: 185
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: 95
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: 184
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: 167
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: 167
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: 1158
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: 398
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: 1158
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: 1158
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...
- Fri Apr 05, 2024 2:52 pm
- Forum: Dumble Discussion
- Topic: ODS Inspired Build; #102 Values with Buffered FX Loop
- Replies: 20
- Views: 844
Re: ODS Inspired Build; #102 Values with Buffered FX Loop
Same as an HT winding where the CT is grounded, the voltages at the opposite ends of the coil are out of phase. The one that is out of phase with the secondary shows a higher voltage because its sine wave is high when the one at the secondary hot is low. Ahh, the voltmeters are with respect to the ...
- Fri Apr 05, 2024 12:17 am
- Forum: Dumble Discussion
- Topic: ODS Inspired Build; #102 Values with Buffered FX Loop
- Replies: 20
- Views: 844
Re: ODS Inspired Build; #102 Values with Buffered FX Loop
My thinking is both voltages should be the same, any idea what the mechanism is that causes them to differ like that?
- Thu Apr 04, 2024 10:17 am
- Forum: Technical Discussion
- Topic: Deluxe Reverb Build
- Replies: 20
- Views: 703
- Wed Apr 03, 2024 1:20 pm
- Forum: Fender Discussion
- Topic: Deluxe Reverb power transformer change?
- Replies: 16
- Views: 1381
Re: Deluxe Reverb power transformer change?
Derek at Watford Valves advises that the Philips ECG WGB run fine in pretty much any guitar amp, even the crazy high voltage late 70s Fenders.
And a mere £50 each!
He better puts his prices up before they migrate back across the pond
https://watfordvalves.com/product_detail.asp?id=1313
And a mere £50 each!
He better puts his prices up before they migrate back across the pond
https://watfordvalves.com/product_detail.asp?id=1313
- Mon Apr 01, 2024 5:32 pm
- Forum: Technical Discussion
- Topic: Lead Dress for Star Grounding
- Replies: 5
- Views: 224
Re: Lead Dress for Star Grounding
... The PT centertap wire to the negative of the first filter cap has big and pulsed (containing higher harmonics) currents running on it. Run that one short and direct, and don't cluster it up with anything else. ... Just to confirm and clarify, the CT of the high voltage winding should be directl...
- Mon Apr 01, 2024 10:28 am
- Forum: Technical Discussion
- Topic: Blackvibe 6L6 Strange behavior on tone pots
- Replies: 17
- Views: 511
Re: Blackvibe 6L6 Strange behavior on tone pots
... On any blackpanel amp if you turn all the tone pots to 0 ... Fender knobs for these amps are 1-10, no 0 available, CCW = 1, CW = 10. ... 6k8 resistance to ground, like a 10kA mid pot set at ~3:00. With a regular 1-10 knob and 10k log pot, I recall a fairly high setting is required, maybe around...