Sound City 100 Mk3 - Master volume

20 Studio, 50+, 50PA, 50R, L100, B100, L120, L120PA, L120R, 120 SLAVE, B120, B150, L150, L200, B200, Concord, and SMF

Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Tue Aug 30, 2016 9:46 pm

Hi everyone,

I have a Sound City 100 and I want to put a Master Volume into the circuit!

I won't destroy the original faceplate, I've preserved it as its in immaculate condition and have made a new one ready for the Master Volume.

I know it's a case of replacing the 1M ohm resistor on the grid of V3.

Can anyone help me out as firstly I want to make sure that the preamp valves run from left to right looking at front
V1 V2 V4 V3 - is this so with these amps?

Secondly can anyone draw on the schematic for me how to solder into the circuit the master volume potentiometer please!?!?

I do not want to do it wrong and I'm just making sure I do it right with my very very basic knowledge of electronics

Kindest regards in advance

Justin
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Wed Aug 31, 2016 2:29 pm

Does anyone have a B100 Circuit with Reverb??

I'm stuggling to know where to put the Master Volume in the circuit - is anyone able to help in anyway?

Regards

Justin
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Dean Jr. on Wed Aug 31, 2016 8:53 pm

Here are some schematics...

http://schematicheaven.net/bargainbin.html

There are a few ways to insert a MV circuit. IMho, it is not something that a beginner should attempt.
YOu might read through this thread on EL-34 World....plus some of the suggested links in there. The method that you are proposing is not one that I would use. It is discussed in this thread....as well as some other options.

http://el34world.com/Forum/index.php?topic=3496.0
Dean Jr.
Page
 
Posts: 314
Joined: Fri Apr 24, 2015 7:59 pm

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Wed Aug 31, 2016 9:28 pm

Thank you Dean Jr for taking the time to reply - much appreciated!!

I'm still deciding whether a pre phase or post phase would be better? What I want is something that doesn't change tone too much but I want to be able to drive amp if required - early Hiwatt style!!

What I need to know is where it goes into my circuit in my amp - SC B100 Mk3 with reverb

Regards Justin
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Papa Dog on Wed Aug 31, 2016 9:52 pm

sheesh....if you need schematics

B100

Image
There Ain't No Such Thing As A Free Lunch.

"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--"
Papa Dog
Knight
 
Posts: 1337
Joined: Mon Mar 15, 2010 6:48 pm
Location: Narly Ampwerks

Re: Sound City 100 Mk3 - Master volume

Postby Papa Dog on Wed Aug 31, 2016 10:00 pm

The Hiwatts wrote:Does anyone have a B100 Circuit with Reverb??

I'm stuggling to know where to put the Master Volume in the circuit - is anyone able to help in anyway?

Regards

Justin


the "correct" placement would be between the coupling cap off the treble control and pin 7 v3 (the grid on v3a) in place of the 1meg resistor.
wiring it up is fairly easy.
some folks swear by PPIMV some swear at it. I fall into the later category. Do NOT like PPIMV. The effect gained is called "power tube distortion" but is actually only phase inverter overdrive. The hardest worked tube in an amp, and folks want to go and push it harder?
To each his own. YMMV
There Ain't No Such Thing As A Free Lunch.

"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--"
Papa Dog
Knight
 
Posts: 1337
Joined: Mon Mar 15, 2010 6:48 pm
Location: Narly Ampwerks

Re: Sound City 100 Mk3 - Master volume

Postby Dean Jr. on Wed Aug 31, 2016 10:26 pm

Confucius would thrown up his hands and watch people die of starvation while the fish swam freely in the waters.

good luck with it all. :jam:
Dean Jr.
Page
 
Posts: 314
Joined: Fri Apr 24, 2015 7:59 pm

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Thu Sep 01, 2016 12:16 am

On my amp the reverb section also comes off Pin 7 on V3 and the 0.004 capacitor???

Can I just disconnect the 2 wires to the reverb and put in my 1M potentiometer here??

My 0.004 cap is not connected to Pin 7 on V3 either like the above circuit???

Can anyone shed any light on this - this is why I'm confused and asking

Justin
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Papa Dog on Thu Sep 01, 2016 1:41 am

The Hiwatts wrote:On my amp the reverb section also comes off Pin 7 on V3 and the 0.004 capacitor???

Can I just disconnect the 2 wires to the reverb and put in my 1M potentiometer here??

My 0.004 cap is not connected to Pin 7 on V3 either like the above circuit???

Can anyone shed any light on this - this is why I'm confused and asking

Justin

can you post pics?
unfortunately I do not have any Mk3 100 with reverb schematics. I do not know where there is any such beast.
Pics would help.
There Ain't No Such Thing As A Free Lunch.

"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--"
Papa Dog
Knight
 
Posts: 1337
Joined: Mon Mar 15, 2010 6:48 pm
Location: Narly Ampwerks

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Thu Sep 01, 2016 8:01 am

Here is an Image with some notes I made of the Pin 7/V3 area of the amp!!!
Image
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Papa Dog on Thu Sep 01, 2016 1:24 pm

that helps.
so, it is not an actual reverb circuit but the reverb "loop"?
If that is the case their is either a cap or jumper between those "sockets" (commonly called "jacks")
pics of the chassis and more gut shots, where I can see the reverb jacks and etc would help.

I am going out on a limb here, but I think that you could replace that 1 meg resistor with a pot, wiper to pin 7, and it would work, but I would like to see the other pics before committing to that.
There Ain't No Such Thing As A Free Lunch.

"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--"
Papa Dog
Knight
 
Posts: 1337
Joined: Mon Mar 15, 2010 6:48 pm
Location: Narly Ampwerks

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Thu Sep 01, 2016 2:55 pm

Thank you Papa Dog!! Appreciate you taking the time to help!!!

We have established remove 1M Resistor
Wiper of 1M pot onto Pin 7

I need to know where other side of pot is wired

and then Ground the pot on the 3rd leg of Pot!!!

Here is an internal shot

Image
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Dean Jr. on Thu Sep 01, 2016 3:50 pm

IT is interesting to compare the schematics for the LB-100 and the 120, which has reverb. I do not see that pin 7 is part of the reverb circuit in the 120. Pin 2 is. I would suggest tracing things out there before making a move. YMMV.

http://schematicheaven.net/bargainbin/s ... y_100b.pdf

http://schematicheaven.net/bargainbin/s ... 20_miv.pdf
Dean Jr.
Page
 
Posts: 314
Joined: Fri Apr 24, 2015 7:59 pm

Re: Sound City 100 Mk3 - Master volume

Postby The Hiwatts on Thu Sep 01, 2016 4:10 pm

Dean Jr: the capacitor 0.004 goes to the treble pot as per the diagram, but is not connected to pin 7 as the circuit, unless it goes the the reverb loop?? But using a multimeter it doesn't seem to do that either? ?

Without a circuit diagram or someone who knows what they are doing I'm a bit stumped

I do think we have established that pin 7 is in fact where we are suggesting it is!!

Justin
"The Place is really jumping to The Hiwatt amps.."
FACEBOOK GROUP: "THE HIWATTS"
The Hiwatts
Squire
 
Posts: 930
Joined: Wed Dec 01, 2004 8:01 am
Location: Southampton, England

Re: Sound City 100 Mk3 - Master volume

Postby Dean Jr. on Thu Sep 01, 2016 4:37 pm

Justin, the ohmmeter can tell you how the circuit is arranged there.....as you go, draw it out. Learning is. IF you are going to work on these things, then learning how to see that circuit in front of you and translate it to and from the schematic is advantageous.
re: my earlier reference to Confucius was this....something like 'give a man a fish, feed him for one day. Teach a man to fish, feed him for a lifetime.'. You can figure that out and solve your problem while learning how to translate from/to the schematic. You have the layout in front of you...it is that circuit in that amp. IF your amp does not match that circuit, then you will learn that, too.
Dean Jr.
Page
 
Posts: 314
Joined: Fri Apr 24, 2015 7:59 pm

Next

Return to Sound City

Who is online

Users browsing this forum: No registered users and 1 guest