It is currently Mon Mar 16, 2020 10:50 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 191 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 13  Next
Go to page Previous  1, 2, 3, 4, 5 ... 13  Next
Author Message
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Tue Aug 04, 2015 8:56 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
I still have those 350 watt eminence bass speakers in there that the last owner had installed when those CTS died.

Won't sound good but at least i can play it while waiting.

The guys at Weber are the best ! and hey they are right here in my own state, I have heard great stuff from the orange County guys too.
The trip I took earlier this year that took me to Kokomo gave me an hour to stop in at Weber and hang out, it revealed what I had assumed about Weber, real players that love making music and really care about their customers.

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Wed Aug 05, 2015 6:32 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Well.............................
New filter caps and bias done to BF specs
468 Volts on the 6L6's
Bias pot maxed out and only 29ma draw on the tubes ???
I've tried several pairs of tubes and can't get up to my magic 33ma

I have not replaced the electrolytic on the bias board so...............

Also wondering how safe a GZ34 would be in there ??? Voltage too high possible ?

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Wed Aug 05, 2015 7:09 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Not drawing enough current could be too much negative voltage coming from the bias supply. If the bias circuit is original one, you have a balance-pot adjustment circuit. Measure the voltage at the second 50mfd/70VDC cap in the bias supply (see schematic). Have pot at mid-point, no 6L6GC tubes inserted, volumes at zero, no input.

Should be -48VDC (+/- 2-3VDC). If the readings are -55VDC or more, you have an over-biased supply. Maybe due to out-of-spec 1K-ohm dropping resistor, off the single bias supply diode. Or weak 50/70 caps. Or both.


Good luck! Think this maybe a quick fix.


BTW.... GZ34 or 5U4GB are fine. Just measure the resultant plate voltages and compensate.

BTW#2... I would convert the balance pot to a bias pot circuit.


http://bmamps.com/Schematics/fender/sup ... _schem.pdf


Balance to bias circuit conversion:

http://el34world.com/charts/bias_conversions.htm


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Wed Aug 05, 2015 8:00 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Balance pot conversion was the first thing I did

I'll check the bias board and replace the electrolytic there also

I'll probably go with the GZ34, I'll let ya know how it works out

I am only running 2 8 ohm speakers at 4 ohms till the other CTS get back from weber.

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Wed Aug 05, 2015 9:35 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
measured -48.1 but that was with 6L6's in place
all pots were at zero

Weird that my readings are within spec and three pairs of 6L6GC cant get past 29 ma ????

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Thu Aug 06, 2015 8:19 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Follow up on the bias
I had a spare GZ34 laying around and so I plugged it in
Now my bias range is 33ma with 1/4 range left over on the bias pot
The PT may be older (too much goo on the bottom to date ) wonder if its a mid to late 60's PT ???
That would make sense as the amp seems to want the 5AR4 instead of the 5U4GB

I'll check plate voltages next trip down

The other CTS will need reconed too :cry: I'm getting a bit of rattle with the volume at 3 , however i'm only running two right now so.............................. we shall see

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Fri Aug 07, 2015 6:14 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
The GZ34 only raised the voltage on the 6L6's by 4 volts to 472 volts
and gave me all the travel I need to get my power tubes where i want them

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Fri Aug 07, 2015 6:35 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Chris, Sorry for late reply. The 5U4GB may not have been passing the current needed to run the 6L6GCs in the proper idle current range. Anyhow, the GZ34 is healthy enough. Good thing you have a good one.

Was that 5U4GB the NOS Tungsol?


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Fri Aug 07, 2015 7:53 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
I tried two a sylvania and a Japan made Raytheon
Both were identical in specs

I shorted an RCA plug to try the vibrato , it works but it's effect is very mild

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Fri Aug 07, 2015 10:54 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Chris,

I have some NOS black plate TS 5U4GB (USA) that make about same B+ as a good GZ34, if you are interested... email me.


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Sat Aug 08, 2015 7:15 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Thanks Beemer !
Dude it sounds so good and runs so quiet, I really hate to change a thing !! :D

And that is still running just two Speakers !
The other two won't be home for a while so i'm keeping the volume around two so I don't mess up the ones in the amp, I will probably just have them reconed also.

So glad to find a non master volume Super ! The guy who sold it to me says big amps are going out of style, i say their coming back, little single 12's just cant do what 4X10 can 8)

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Sat Aug 08, 2015 6:35 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Chris,

Don't change anything. If the thing bias-up ok & sounds fine --- let sleeping dogs lie.

:lol: :mrgreen:


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Wed Aug 12, 2015 11:40 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Image

Now on the the Phase inverter
82K on the left 100K on the right and 1M on either side of the long tail

New 25uf 25Volt electrolytics throughout the board eventually

Oh and the .01 cap on the PI will be .001 and a mallory 150 instead of the ceramic cap

Got a nice pair of GE 1960's 6L6GC's coming too

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Thu Aug 13, 2015 7:26 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Chris,

Why did you go to a 0.001 mfd cap versus the stock 0.01 mfd disc cap?


Top
Profile
Post subject: Re: Road worn 1974 Super Reverb restoration
Posted: Thu Aug 13, 2015 7:41 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Bringing it back to blackface specs
Supposedly enhancing the bass response

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 191 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 13  Next
Go to page Previous  1, 2, 3, 4, 5 ... 13  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 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

Search for:
Jump to: