Search found 2688 matches

by pdf64
Sun Mar 24, 2024 12:29 am
Forum: Technical Discussion
Topic: Heater Wire Ground
Replies: 30
Views: 407

Re: Heater Wire Ground

(1) And the heater center taps are sometimes not too accurate. A couple of resistors may well make a better center tap, with lower induced hum. Why do you think that the minimum hum is on the middle of very- too much precision- resistors ? Give us some technical reference and measurement. 8) I've n...
by pdf64
Sat Mar 23, 2024 1:15 pm
Forum: Technical Discussion
Topic: Bias range question.
Replies: 27
Views: 506

Re: Bias range question.

You should start with the bias voltage at the most negative setting (largest number). Talking about negative voltage is always confusing. The convention I follow is more negative is lower, which is mathematically correct and follows the convention for temperature. I still write it two ways to make ...
by pdf64
Thu Mar 21, 2024 11:57 pm
Forum: Fender Discussion
Topic: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?
Replies: 10
Views: 253

Re: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?

Yes, all the silverface 70 and 135 watt amps where Ul and as such not what you want it your looking for a true Deluxe playing feel and response . To describe those OTs / output stages as UL implies that their design has been optimised for linearity. As the taps are at about 12.5%, my understanding ...
by pdf64
Thu Mar 21, 2024 7:03 pm
Forum: Speakers and Cabinets
Topic: Cabinet made of OSB instead of pine
Replies: 13
Views: 400

Re: Cabinet made of OSB instead of pine

chaccmgr wrote: Thu Mar 21, 2024 1:35 pm ...
almost everybody uses 18mm/1/2" plywood today, if reinforced, you might get away with 15mm
...
Just to note that rather than 1/2", I think the imperial equivalent of 18mm is 3/4" :)
by pdf64
Thu Mar 21, 2024 3:02 pm
Forum: Fender Discussion
Topic: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?
Replies: 10
Views: 253

Re: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?

Reeltarded wrote: Thu Mar 21, 2024 2:11 am Isn't this a late silver model with UL taps on output?
Not from those transformer codes, they match this earlier version https://el34world.com/charts/Schematics ... man_10.pdf
Still super high HT voltage though.
I seem to recall that the OT there is surprisingly wimpy.
by pdf64
Thu Mar 21, 2024 1:17 pm
Forum: Technical Discussion
Topic: Is there a way to measure the amount of supply current in the 2nd tabs of the Power Transformer?
Replies: 6
Views: 152

Re: Is there a way to measure the amount of supply current in the 2nd tabs of the Power Transformer?

The transformer was designed to cope with 6.3x3= 18.9VA load on that winding. There might be another 150VA load from the HT winding? The total max load might be 170VA. You're wondering whether it'll cope with increasing the heater winding load to 6.3x4.2=26.5VA. The total max load might then be up n...
by pdf64
Thu Mar 21, 2024 12:43 am
Forum: Technical Discussion
Topic: Input requested: Matchless Chieftain build (with original and modified schematics included)
Replies: 6
Views: 625

Re: Input requested: Matchless Chieftain build (with original and modified schematics included)

https://makeabilitylab.github.io/physcomp/electronics/assets/images/Potentiometers_TwoExamplesWithSchematicSymbol.png My understanding is that a regular volume control would wire lug 1 to common, 3 to signal in, 2 to signal out. Schematics usually arrange things so that as the wiper is moved up, th...
by pdf64
Wed Mar 20, 2024 8:48 am
Forum: Fender Discussion
Topic: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?
Replies: 10
Views: 253

Re: Can I use a Bassman 70watts PT and OT for a Deluxe reverb?

It depends how closely you want your build to comply with the design of a Deluxe Reverb. On the face of it, neither transformer aligns with the DR spec. Why have you chosen a DR, rather than eg a Super Reverb 70 https://el34world.com/charts/Schematics/files/Fender/Fender_cbs_70w_mstrvol_pullsw_super...
by pdf64
Fri Mar 15, 2024 10:53 am
Forum: Technical Discussion
Topic: V1 split cathode
Replies: 14
Views: 328

Re: V1 split cathode

Rather than just isolted photos of just the board or V1 socket, it may be helpful to provide photos that add up to provide a complete picture of what you're got there. Whatever, as only half of (what I assume is) the V1 socket has ever been wired up, it seems that it's a single channel amp, probably...
by pdf64
Mon Mar 11, 2024 11:35 am
Forum: Technical Discussion
Topic: Help with circuit
Replies: 18
Views: 349

Re: Help with circuit

... I get it just wanted to get a presence control in there but somehow the robrob version of it canceled out all the guitar signal... Detail, both in design (eg schematic) and implementation (layout and actual build) is critical in this game. Making vague references to things you've done as per ab...
by pdf64
Sun Mar 10, 2024 1:41 pm
Forum: Technical Discussion
Topic: Help with circuit
Replies: 18
Views: 349

Re: Help with circuit

... The 470k resistor is missing because I got the wrong value ... I guess you're referring to the missing V3 LTP cathode bias resistor? Its typical value is 470 ohms. A 470k resistor is 470,000 ohms. At the V1 end of the board there's a 270k resistor. If that's intended to be a cathode bias resist...
by pdf64
Fri Mar 08, 2024 1:05 am
Forum: Technical Discussion
Topic: 2024 Monkeymatic Liverpool (nontraditional)
Replies: 48
Views: 1207

Re: 2024 Monkeymatic Liverpool (nontraditional)

I think of that tonestack as being a variant of the Gibson / Vox https://el34world.com/charts/Schematics ... nguard.pdf
by pdf64
Tue Mar 05, 2024 11:33 am
Forum: Technical Discussion
Topic: Output transformers
Replies: 10
Views: 260

Re: Output transformers

strat100 wrote: Tue Mar 05, 2024 11:03 am Sorry forgot to mention it's got a pair of 6v6s
No problem, the HT may need to be a bit stiffer, eg bigger reservoir cap.
Image
by pdf64
Tue Mar 05, 2024 10:00 am
Forum: Technical Discussion
Topic: Output transformers
Replies: 10
Views: 260

Re: Output transformers

My understanding is that a core that's good for 10W at 30Hz should be good for 20W at 60Hz, 40W at 120Hz etc. Obviously the windings overheating will become a limitation at some stage. I guess your amp is a copy of a DS mini, using a push pull pair of EL84? I've read posts from builders successfully...
by pdf64
Thu Feb 29, 2024 12:52 pm
Forum: Technical Discussion
Topic: Does Bias 1 ohm resistor tolerance matter?
Replies: 5
Views: 212

Re: Does Bias 1 ohm resistor tolerance matter?

Shorting the meter probes together prior to measuring any resistance is a basic sanity check.