Search found 226 matches

by gldtp99
Wed Mar 27, 2024 11:53 am
Forum: Marshall Discussion
Topic: 2204 build voltages are off
Replies: 9
Views: 220

Re: 2204 build voltages are off

Here is a schematic (w/voltages) of one 1983 Marshall 2204 (owned by mhuss) These are typical voltages of a 1983-era 2204 amp --- This does not mean that EVERY 1983 2204 will match these voltages exactly --- this does not mean that EVERY Marshall 2204 ever made will match these voltages (my '79 Mars...
by gldtp99
Sun Mar 03, 2024 1:03 am
Forum: Marshall Discussion
Topic: Sir 36 mod
Replies: 10
Views: 622

Re: Sir 36 mod

Years ago I followed some of the many SIR #36 schematics you posted (on another forum) and built many similar amps, usually 50 watt These heads were sold to musicians in my local area and were well received --- your schematics helped me to learn to modify Marshall circuits But most local musicians, ...
by gldtp99
Mon Feb 12, 2024 3:45 am
Forum: Marshall Discussion
Topic: '82 JCM800 2204
Replies: 4
Views: 569

Re: '82 JCM800 2204

I did some tweaking to a 25 watt 2204-type build I did recently --- I put the 470k/470pF !st Treble Peaker back in (i had a 68k in there) to give it more treble response when the MV is cranked above 5 --- this worked well, I'd gotten into the habit of building 2204-type amps without the 1st Treble P...
by gldtp99
Thu Feb 01, 2024 5:58 pm
Forum: Marshall Discussion
Topic: '82 JCM800 2204
Replies: 4
Views: 569

'82 JCM800 2204

I recently serviced this amp for a friend --- It is a 6550 spec amp that had EL34's installed (which biased the EL34's so cold that it barely operated at all) I quickly measured all the resistors in the amp (initially looking for the "problem" before I realized it was a 6550 amp) and I found that th...
by gldtp99
Fri Jan 19, 2024 3:54 am
Forum: Technical Discussion
Topic: Sound City L120 mk4 Biasing
Replies: 10
Views: 1210

Re: Sound City L120 mk4 Biasing

Here's a 100 ohm/5 Watt Metal Oxide Power Resistor that Mouser currently has in stock --- It has better specs than the other 3 similar resistors they have right now: https://www.mouser.com/ProductDetail/YAGEO/RSF500JT-91-100R?qs=sGAEpiMZZMvmQ%252BOLa8n%2FM0VaQqJq%2FX2CratbCum5YeFYTqqG54ZAZA%3D%3D Bu...
by gldtp99
Mon Jun 26, 2023 3:58 pm
Forum: Marshall Discussion
Topic: sv20h circuit question
Replies: 3
Views: 1657

Re: sv20h circuit question

Why not build your own Mini-Plexi ?

I just built two mini-2204's (6L6GC x 2, 25 watt scaled iron) one stock-ish and the other Hi Gain with a plate driven tone stack and other mods

You can build your mini-Plexi and make it however you want it

https://mhuss.com/Plexi6V6/Plexi6V6.gif
by gldtp99
Mon Oct 31, 2022 8:35 am
Forum: Vox/Hiwatt Discussion
Topic: Tube shield in a Hiwatt?
Replies: 16
Views: 4339

Re: Tube shield in a Hiwatt?

I built two DR504 clones in 2006 without heat shields ---- One I still have and it is still running fine --- The other was sold to a touring band that has been using it since then playing all over the SW USA, Mexico, and parts of South America --- They brought it back to me once for a "tune up" and ...
by gldtp99
Sun Aug 28, 2022 12:22 am
Forum: Fender Discussion
Topic: carbon comp resistors
Replies: 49
Views: 6771

Re: carbon comp resistors

I just saw a YT video that said Reptilian Space Aliens have a military base in Antarctica from which they fly most of the craft that people report as UFO's It went on to say that they've been having navigation problems (because they're Space Aliens) and have hired Elvis Presley to pilot their craft ...
by gldtp99
Fri Mar 11, 2022 5:47 pm
Forum: Fender Discussion
Topic: 1965 Bandmaster hum
Replies: 93
Views: 11989

Re: 1965 Bandmaster hum

I must agree If the OP's amp has Stray Voltage on the main Eyelet Board then no parts swapping will fix the hum problem until the Stray Voltage is eliminated I'd also take a very close look at the grounding of everything on the front panel of the amp ----- Make sure everything is Clean, Tight, and S...
by gldtp99
Sun Mar 06, 2022 8:49 pm
Forum: Fender Discussion
Topic: 1965 Bandmaster hum
Replies: 93
Views: 11989

Re: 1965 Bandmaster hum

No, just the rectifier diodes ---- not on the Main Board

It seems like I've seen this black paint/dye on other old BF Fender amps, too

Maybe on the many Showman/Dual Showman amps i've owned or serviced
by gldtp99
Sun Mar 06, 2022 5:39 pm
Forum: Fender Discussion
Topic: 1965 Bandmaster hum
Replies: 93
Views: 11989

Re: 1965 Bandmaster hum

My #2 '65 Bandmaster had the black dye/paint on the diode solder joints, too ---- I just un-soldered the joints as usual and used my vacuum pump to clean out all the old junk ---- I removed the Rectifier/Bias board and backing board and cleaned up everything before i put it all back together with ne...
by gldtp99
Sun Mar 06, 2022 12:42 am
Forum: Fender Discussion
Topic: 1965 Bandmaster hum
Replies: 93
Views: 11989

Re: 1965 Bandmaster hum

I installed new 1N4007's in the rectifier (Bias, too) when I got my #2 '65 Bandmaster up and running when I first got it I re-did the whole Rectifier/Bias board when I replaced the blown PT it came with When I tested this one out it sounded almost as good as my #1 '65 Bandmaster (my favorite amp) so...
by gldtp99
Thu Dec 23, 2021 9:10 pm
Forum: Marshall Discussion
Topic: output section for small venues - JCM800
Replies: 12
Views: 2373

Re: output section for small venues - JCM800

Years ago I built an EL84 x 2 2204 type head and ended up installing both the pre-PI MV and a PPIMV Also added a fixed Resonance/Depth circuit and added a bit of extra gain to the preamp (and cutting some low freqs in preamp to counter higher gain flubbiness) I still have this one and it is useful a...
by gldtp99
Mon Nov 29, 2021 12:34 pm
Forum: Technical Discussion
Topic: Sound City L120 mk4 Biasing
Replies: 10
Views: 1210

Re: Sound City L120 mk4 Biasing

I've Rebuilt/Reporposed dozens of SC 120's over the years ---- Hiwatt preamps, Modern Hi Gain preamps, Blackface/Brownface Fender preamps To help out the sometimes marginal Bias Supply, I've taken to installing 100 ohm/5 watt Cathode resistors on all six Output tubes Then building a Hiwatt DR103 typ...
by gldtp99
Thu Sep 17, 2020 7:18 am
Forum: Technical Discussion
Topic: Silver tone 1485 build
Replies: 20
Views: 1837

Re: Silver tone 1485 build

I question why the OP has picked a Silvertone 1485 as his first build. I have a 1485 that I've had for many years, restoring it back into a safe player early in the process----- I've rebuilt/serviced many 1484's (and other old Silvertones) so I'm pretty familiar with these amps. I'd suggest the OP f...