Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Mr_Tickle on May 03, 2012, 02:09:41 pm

Title: Jcm 800 2203 new build
Post by: Mr_Tickle on May 03, 2012, 02:09:41 pm

Hi there.
I am just about to start my build and am getting slightly confused as to differing info regarding connections to the EL34's.
The schematic I have shows pins 4 and 6 connected through a 1K 5 watt resistor and pin 5 going to the board via a 5.6k resistor yet looking at the Hoffman Plexi layout on the site it says pins 5 and 6 connected through the 5.6k resistor and pin 4 to the board through a 1k ressistor.
Are they both correct? If so what difference does it make?
May be silly questions but I am learning as I go and dont want to cock it up.
Cheers

Title: Re: Jcm 800 2203 new build
Post by: jerrydyer on May 03, 2012, 02:33:20 pm

its just a preference. 6 is nothing so Doug chooses to use 6 as a connection point for the 5.6k resistor to pin 5. And he prefers his 1k 5watts on the board.... dats all.

Title: Re: Jcm 800 2203 new build
Post by: sluckey on May 03, 2012, 04:04:45 pm

What he said. But here's a tip. Get one schematic/layout to work with and don't look at others. Stay with the one and let the other one ride. There's always more than one way to skin a cat, and you may get into trouble switching between different layouts for the same amp. But......

Hoffman's Plexi ain't the same as a JCM-800 2203.

Title: Re: Jcm 800 2203 new build
Post by: jerrydyer on May 03, 2012, 04:06:44 pm

yep...I dont know how many bonehead mistakes ive made like that.

Title: Re: Jcm 800 2203 new build
Post by: Fresh_Start on May 03, 2012, 09:13:13 pm

When in doubt, there's no substitute for the tube data charts:
http://www.mif.pg.gda.pl/homepages/frank/vs.html (http://www.mif.pg.gda.pl/homepages/frank/vs.html)

Cheers,

Chip

Title: Re: Jcm 800 2203 new build
Post by: Mr_Tickle on May 04, 2012, 02:29:06 am

Thanks for the info guys.
I agree with Sluckey. I'll stick to one schematic and stop look on the web.
AND I know pin 6 doesn't do anything so WHY didnt I work that one out myself. DOH!!!!!!! :l2:
Anyway you live and learn.

I'll probably be on again soon with more questions as this sight is great with tons of knowledge on it so I better stop reading and get soldering.

Cheers again

Title: Re: Jcm 800 2203 new build
Post by: jerrydyer on May 04, 2012, 11:30:12 am

brain fart
one time I was tired and I sat there for 5 minutes with buss wire against my solder tip getting angry that it wasnt melting...  :laugh:

Title: Re: Jcm 800 2203 new build
Post by: TubeGeek on May 12, 2012, 02:20:46 pm

Quote from: jerrydyer on May 04, 2012, 11:30:12 am

brain fart
one time I was tired and I sat there for 5 minutes with buss wire against my solder tip getting angry that it wasnt melting...  :laugh:

Been there, done that too!

Title: Re: Jcm 800 2203 new build
Post by: Davidg on May 13, 2012, 12:59:54 am

I had to learn a lesson like that today! I have had an old Traynor YGL3 mk3 I have been tinkering with for a couple of months- tried every possible combination of tone stack values and the amp always sounded like crap-very nasally, icepick treble.Finally realized the tone controls were wired wrong and had been since I had the amp :think1:! That was not being tired but plain old not paying attention

Title: Re: Jcm 800 2203 new build
Post by: Willabe on May 13, 2012, 09:02:00 am

How does it sound now?


               Brad      :icon_biggrin: