Search found 178 matches

by SoulFetish
Sat Dec 09, 2023 4:59 pm
Forum: Technical Discussion
Topic: failed diode / PT question
Replies: 12
Views: 3250

Re: failed diode / PT question

I had an older MIG50 in with a blown soviet era bridge rectifier just last month... Not sure sure why they would be more prone to failure than anything else, the B+ is high, but not that high. Probably just a coincidence. I watched a video recently about someone getting counterfeit voltage regulato...
by SoulFetish
Sat Dec 09, 2023 2:53 pm
Forum: Technical Discussion
Topic: Conjunctive filter
Replies: 18
Views: 3689

Re: Conjunctive filter

In RDH4, Smith provides some examples. You might find that helpful in combination with some of the concepts teemuk was explaining.
Here is a screenshot of page 588.
Screenshot 2023-12-09 at 09-46-24 Radiotron Designer's Handbook 4th Edition - rdh4.pdf.png
by SoulFetish
Sat Dec 09, 2023 2:38 pm
Forum: Technical Discussion
Topic: failed diode / PT question
Replies: 12
Views: 3250

Re: failed diode / PT question

just curious, where did you buy you UF5408s? A few weeks back a customer came in with a newer model Sovtek MIG 50 with a blown mains transformer. Even though it was out of warranty, they replaced the PT, no cost to customer. It turns out that a shorted 1N5408 probably took the transformer out (usual...
by SoulFetish
Fri Dec 08, 2023 9:03 pm
Forum: Technical Discussion
Topic: Just when I thought I had come to understand OT secondaries,,,
Replies: 25
Views: 7366

Re: Just when I thought I had come to understand OT secondaries,,,

like the others, I don't make this measurement using resistance. I use my signal generator and my oscilloscope. It's very safe and very accurate, even applying lower voltages to the primary. My signal generator can output an undistorted 10V p-p sine wave, and my o-scope can list and measure RMS, Pea...
by SoulFetish
Thu Jul 20, 2023 3:19 am
Forum: Technical Discussion
Topic: Midpot to 50k and a question
Replies: 11
Views: 1063

Re: Midpot to 50k and a question

One small change... Instead of saying "yellow/purple/orange", you should say "yellow/violet/orange". Purple is not on the color charts. :mrgreen: My professors in art school, would roll her eyes and correct any one who called it color "purple", and say "there's no such color as purple. You mean 'Vi...
by SoulFetish
Sun Jul 09, 2023 10:12 pm
Forum: Technical Discussion
Topic: Copel Rotary Switch
Replies: 2
Views: 285

Re: Copel Rotary Switch

I don't have any experience with the Copel switch, but last time I looked, pickings were getting really slim for heavy duty rotary switches we can use as impedance selectors. NKK discontinued many of their nice rotary switches a couple of years ago, and they were the diy industry standard and good q...
by SoulFetish
Sun Jul 09, 2023 9:45 pm
Forum: Technical Discussion
Topic: Calibrating gain stages
Replies: 7
Views: 815

Re: Calibrating gain stages

I would just add that how each gain stage is biased makes a huge difference in how the amp sounds, and responds at the beginning of clipping through heavy overdrive (as well as if a particular stage has a cathode bypassed or not). For instance, if you set up you test circuit with trim pots for catho...
by SoulFetish
Sat Jun 03, 2023 5:49 am
Forum: Technical Discussion
Topic: Help with dropping B+ with Zeners
Replies: 33
Views: 1909

Re: Help with dropping B+ with Zeners

I would be surprised if RG doesn't jump in on this topic and express that you can use his zener/mosfet combination (from mosfet follies ver...1?) to great effect for your purposes. It is simple, effective, inexpensive, and I used it in a amp I built incorporating 2 EL84s and 3 12AX7s. For that build...
by SoulFetish
Tue Apr 11, 2023 9:37 pm
Forum: Technical Discussion
Topic: too much hum
Replies: 15
Views: 1598

Re: too much hum

Oh yeah. I shorted the input
by SoulFetish
Tue Apr 11, 2023 9:36 pm
Forum: Technical Discussion
Topic: USA Vacuum Tube Manufacturing Revival
Replies: 16
Views: 1237

Re: USA Vacuum Tube Manufacturing Revival

ViperDoc wrote: Thu Mar 30, 2023 9:40 pm What a great article. Have you ever seen a more beautiful tube than the 300B at the top of the page? (I know, tubes are so subjective! :lol: )
I want to build a pedal and use 300Bs as clipping diodes.
by SoulFetish
Tue Apr 11, 2023 9:28 pm
Forum: Technical Discussion
Topic: too much hum
Replies: 15
Views: 1598

Re: too much hum

This manifested itself in a kind of noise that had a very "buzzy" kind of quality In my amp (even with the heater wiring and lead dress being being solid). Did you get this buzz with master on zero? Well, I don't have a traditional master volume on my amp. There is just a single volume, however, wi...
by SoulFetish
Tue Apr 11, 2023 1:29 am
Forum: Technical Discussion
Topic: too much hum
Replies: 15
Views: 1598

Re: too much hum

Without touching on all the potential causes of hum issues, maybe I can help trying to eliminate 2 of them. The first: Easy one, a bad tube can cause noise problems which can sound like a number of different problems. You can start at V1, pulling each tube and listening to whether the tube you pulle...
by SoulFetish
Sat Dec 03, 2022 4:55 am
Forum: Technical Discussion
Topic: Heater wire supplier
Replies: 3
Views: 567

Re: Heater wire supplier

I want to buy by the roll. I'm tired of fighting this. I don't like doing heater wiring and having to search through my rats nest of wire makes it worse. Dude, you're making the right call. You're finally going to be free. I grew so tired and frustrated spending valuable time digging through transf...
by SoulFetish
Mon Jun 06, 2022 2:24 pm
Forum: Technical Discussion
Topic: NTE resistors
Replies: 9
Views: 1131

Re: NTE resistors

They list their 1/2W resistors as metal film. 1,2, & 3W types as Metal Oxide
by SoulFetish
Mon Jun 06, 2022 2:19 pm
Forum: Technical Discussion
Topic: NTE resistors
Replies: 9
Views: 1131

Re: NTE resistors

I think they label those newer ones as flameproof, correct? I think it refers to the coating