Reply to topic  [ 13 posts ] 
Repairing a SoundCity 120 
Author Message
Online
Hall of Fame Member
User avatar

Joined: Sun Jan 20, 2013 9:22 am
Posts: 3522
Location: Manchestoh, UK
Image
A friend had an SC120 that was making all sorts of noise and misbehaving. First notable thing was one of the 6(!!!) EL34s was redplating and was for the bin.

Image
When I pulled the chassis I was greeted by this. Yup, the safety ground and become disconnected, leaving the amp at risk of causing electric shock should there be a short to the chassis and also leaving the circuit floating.


Image
I repaired the safety ground and also added some much needed strain relief with a couple of cable ties behind the cable gland.


Image
I stuck a spare EL34 in and rebiased to around 60%. Ideally I'd want to stick a full fresh set in but that's not an option for my friend right now. The spare I have is matching okay with whats in and the quiescent current on each half of the output transformer is reasonable balanced.

The amp is sat idling for an hour on my bench to test it. I can't crank it right now unfortunately. So far no bad noises or redplating.
The big blue cap in the top of the photo was also secured into the clamp as it had become loose.

I should hopefully be able to drop this back with my friend soon. It'll get cranked of course.

_________________
Loop wrote:
I’m currently shopping for a 1996 Red Dodge Viper with yellow wheels. Who gives a shit about taste?!


Wed Jan 31, 2018 12:41 pm
Profile
Crystal Lettucer
User avatar

Joined: Sat Jul 20, 2013 9:35 pm
Posts: 17663
Location: Same town as Lindsay Lohan, Amy Fisher, Joey Buttafucco & Debbie Gibson
Charge him $400 for Bench Time and $50 for the tube! :lol:

Just kidding!

Man, I'd still have a few old amps if I knew that some issues wer easy to fix.

_________________
1969 Sunn Solarus ● 2x 1980's Randall RG-80 ● 2013 Hi-Tone HT103-DG (Winner Best Rig 2014) ● 2015 Mortatone 12/15 Cab w/EV SRO's ● 2017 Jubilee ● 2019 Ceriatone Model Tee
Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Wed Jan 31, 2018 1:34 pm
Profile
Online
Hall of Fame Member
User avatar

Joined: Sun Jan 20, 2013 9:22 am
Posts: 3522
Location: Manchestoh, UK
Amps aren't that hard to diagnose and repair. Most of the time it's going to be something simple like bad tubes or blown screen grid resistors. After that you're looking at the power supply or bad wiring. Actual wacky shit that takes a lot of effort to figure out is pretty rare.

_________________
Loop wrote:
I’m currently shopping for a 1996 Red Dodge Viper with yellow wheels. Who gives a shit about taste?!


Thu Feb 01, 2018 2:53 am
Profile
Hall of Fame Member

Joined: Mon Apr 23, 2018 10:14 am
Posts: 457
Location: Colorado Springs
ajaxlepinski wrote:
Charge him $400 for Bench Time and $50 for the tube! :lol:

Just kidding!

Man, I'd still have a few old amps if I knew that some issues wer easy to fix.



Every so often if i want to make some cash, I post up on craiglist offering to buy broken tube amps. You would be surprised at the stuff you can get for less then $100 bucks, 90% of the time its something very very simple.


Mon Apr 23, 2018 11:37 am
Profile
Hall of Fame Member

Joined: Tue Jan 22, 2013 9:21 am
Posts: 621
Location: Danbury, CT
trey85stang2 wrote:
Every so often if i want to make some cash, I post up on craiglist offering to buy broken tube amps. You would be surprised at the stuff you can get for less then $100 bucks, 90% of the time its something very very simple.


A few years ago I got a Peavey Ultra Plus for $100 because the guy said it didn't work and he didn't want to bother with it. It ended up being a 12AX7 that needed replacing. Thank goodness for lazy people.

_________________
Amps: 5150 (w/bias mod), 5150 II, EVH 5150 III 50 watt, FJA PV XXX, Framus Dragon, FJA PV Penta, PV Rockmaster-->Marshall 9100, JetCity 20H (2)
Cabs: 3 Marshall 1960B, Marshall 1966B, Avatar 2x15, PV XXX 4x12, misc 2x12's.


Mon Apr 23, 2018 1:09 pm
Profile
Crystal Lettucer
User avatar

Joined: Sat Jul 20, 2013 9:35 pm
Posts: 17663
Location: Same town as Lindsay Lohan, Amy Fisher, Joey Buttafucco & Debbie Gibson
trey85stang2 wrote:
ajaxlepinski wrote:
Charge him $400 for Bench Time and $50 for the tube! :lol:

Just kidding!

Man, I'd still have a few old amps if I knew that some issues wer easy to fix.



Every so often if i want to make some cash, I post up on craiglist offering to buy broken tube amps. You would be surprised at the stuff you can get for less then $100 bucks, 90% of the time its something very very simple.



What a great idea! :idea:
Been studying amp repair as a hobby for a couple of years... I think I need to give this a go right now.
My plan was to supplement my Social Security (when I retire in 10 years) by fixing other people's amps.
But, it never occurred to me to advertise for broken amps to fix and resell.
Cheers!!! :hi5:

_________________
1969 Sunn Solarus ● 2x 1980's Randall RG-80 ● 2013 Hi-Tone HT103-DG (Winner Best Rig 2014) ● 2015 Mortatone 12/15 Cab w/EV SRO's ● 2017 Jubilee ● 2019 Ceriatone Model Tee
Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Last edited by ajaxlepinski on Mon Apr 23, 2018 1:15 pm, edited 2 times in total.



Mon Apr 23, 2018 1:13 pm
Profile
Hall of Fame Member

Joined: Mon Apr 23, 2018 10:14 am
Posts: 457
Location: Colorado Springs
MikeO wrote:
trey85stang2 wrote:
Every so often if i want to make some cash, I post up on craiglist offering to buy broken tube amps. You would be surprised at the stuff you can get for less then $100 bucks, 90% of the time its something very very simple.


A few years ago I got a Peavey Ultra Plus for $100 because the guy said it didn't work and he didn't want to bother with it. It ended up being a 12AX7 that needed replacing. Thank goodness for lazy people.



My best one was a guy that had a fender pro jr. He was so excited to get rid of it he drove it across town to my house and I gave him $20. It intermittently would power off. It was two broken solder joints from the transformer to the board. I had it sold for $300 a day later.


Mon Apr 23, 2018 1:13 pm
Profile
Crystal Lettucer
User avatar

Joined: Sat Jul 20, 2013 9:35 pm
Posts: 17663
Location: Same town as Lindsay Lohan, Amy Fisher, Joey Buttafucco & Debbie Gibson
$280 profit on a couple of drops of solder! Amazing!

_________________
1969 Sunn Solarus ● 2x 1980's Randall RG-80 ● 2013 Hi-Tone HT103-DG (Winner Best Rig 2014) ● 2015 Mortatone 12/15 Cab w/EV SRO's ● 2017 Jubilee ● 2019 Ceriatone Model Tee
Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Mon Apr 23, 2018 1:17 pm
Profile
Hall of Fame Member
User avatar

Joined: Mon Feb 09, 2015 1:48 am
Posts: 2766
Location: Upper Dutchess County NY
I have 4 amps in my collection that were intended to be fix and flip amps. I fixed them all, it's the flip part I seem to have a problem with. :lol:

'65 Danelectro DM10 $50 broken tube (value $150)
'67 Silvertone 1482 $185 loose speaker lead & broken volume pot (value $400)
'59 Stromberg Carlson AU10 $100 bad power switch (value $250)
Peavey 6505+ $275 burned ribbon cable connector (value $450)

The only one I actually fixed & sold was a '70s Earth G1000 head I got for free (Dual Showman clone). It needed some rewiring to replace wires mice had completely eaten and a few tubes from my stash. I sold that for $250.


Tue May 01, 2018 3:36 pm
Profile
Online
Hall of Fame Member
User avatar

Joined: Sun Jan 20, 2013 9:22 am
Posts: 3522
Location: Manchestoh, UK
Alas this amp has now developed another fault and will be back on be workbench when I have time. I'm gonna go through the whole damn amp as it's most likely a bad wire/solder joint that has gone microphonic. SC120's can be a massive pain in the ass!

_________________
Loop wrote:
I’m currently shopping for a 1996 Red Dodge Viper with yellow wheels. Who gives a shit about taste?!


Wed May 02, 2018 3:34 am
Profile
Hall of Fame Member
User avatar

Joined: Mon Feb 09, 2015 1:48 am
Posts: 2766
Location: Upper Dutchess County NY
I feel your pain bro.

Image

There are so many possible rabbit holes to go down under the hood.

Image

I recapped mine then chased ghosts for a few years before giving up and selling it.


Wed May 02, 2018 7:08 am
Profile
Hall of Fame Member
User avatar

Joined: Mon Jan 21, 2013 12:35 pm
Posts: 1035
Riffraff wrote:
I have 4 amps in my collection that were intended to be fix and flip amps. I fixed them all, it's the flip part I seem to have a problem with. :lol:



Brother from another mother!

Do you know how many laptops and desktops I have (and there's only me, wife, and 2 kids)?

I'd much rather be fixing amps!

_________________
After Tuesday, even the calendar goes WTF!


Wed May 02, 2018 11:09 am
Profile
Hall of Fame Member
User avatar

Joined: Fri Jan 18, 2013 4:56 am
Posts: 8724
Location: Corn field in Indiana
I've owned one Sound City head and fixed another plus mine. I will say they are a bitch to troubleshoot. Fucking intermittent problems with both :mad:

_________________
I’d rather smoke crack than eat cheese from a tin.’
-Gwyneth Paltrow


Sat May 11, 2019 5:22 am
Profile
Display posts from previous:  Sort by  
Reply to topic   [ 13 posts ] 

Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  




Powered by phpBB® Forum Software © phpBB Group