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Topic: Repairing a Standel hybrid amp |
Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 8:35 am |
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This is to enlighten those interested on the difference between the Standel hybrids and their solid state counterparts that came out a couple years later.
I hope he doesn't mind but one of our forum members, Stanley Bytrowski, sent me this amp for repair. As you can see, someone decided to remove the can capacitors and do their own little hatchet job before Stanley got it. When Stanley got it (and I received it) there was no sound output out of either channel.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 8:48 am
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Since there was no good way to attach the capacitors that were installed in the amp, I ordered replacement caps where I could use the existing can-cap holes. I had to dismantle all the capacitors and modified wiring and discovered that there were a number of miswires of the power supply. Installed the new capacitors and rewired per the original S100V Power Supply schematic, which was luckily available on the Standel website. With the wiring corrections, the amp was now putting out sound out of both channels. The damage was a lot less severe than suspected. Only the Vibrato module was not working. Was able to verify that the power tubes were shot and that the phase inverter tube was the wrong one. With a regular guitar found that the amp was overdriven at about 3 on the volume. It had a 12AX7 in that position with a gain of 100. Changed to a 12AU7 (gain of 20) and it worked good for humbucker style pickups. With low gain Fender single coils you might be able to get away with a 12AY7.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 9:06 am
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The Red Module of the solid state amps has a driver circuit that drives a lamp that hits a resistor that changes value with the amount of light, just like in the old Fender Blackface amps. In the Standel hybrid amp they used a transformer that worked similar to a ring modulator. The module consists of an oscillator, similar to the one in the Red module, and a driver circuit that feeds one primary of the transformer. The preamp module feeds another primary of the transformer and the secondary then goes to another amp stage before the tone circuits.
I had to play detective on this one, slowly grinding the epoxy away to reveal the traces of the circuit board on one side and the component type on the other. I was able to determine that the oscillator circuit was almost identical to the Red Module but the driver circuit was completely different. Started out with the Red Module values and found I had to change transistor types to get the oscillator working as well as have enough drive to feed the transformer. I then had to change the capacitor values of the oscillator to get the Vibrato speed within a usable range because it was way too fast.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 9:20 am
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Now to the cleanup work!
Replaced the two-prong power cord with a standard 3-prong grounding plug. Tightened all the pins on the tube sockets and replaced the missing tube cover for the 12AU7.
Stanley wanted a way to have multiple impedance taps available for the speakers. I discovered that Standel used the normal ground lead of the output transformer as the hot lead that had feedback to phase inverter. The 16 ohm tap was grounded at the 1/4" jack. I discarded the idea of tap change with plugging into a 2nd jack and found a switch that was rated at 10 amps to put into that open jack hole. The problem was that the depth of the chassis is barely one inch. I had to grind away part of the switch casing to get it to clear the casing. Found that there were 4, 8, and 16 ohm taps available. Put the switch in where it would switch the various taps to ground. Was also able to find a knob to match those on the front.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 9:26 am
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Last one, I promise!
I decided to run a straight edge across the bottom of the amp and found that the two large orange drop capacitors and a power resistor, both visible in the first pictures, were sticking above the chassis. The person that "fixed" the power supply strikes again.
It took some searching but I was able to locate capacitors and a power resistor that had a low enough profile. Tested after replacing them and the amp works fine and is ready to ship back to Stanley!
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Jerry Roller
From:
Van Buren, Arkansas USA
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Posted 5 Apr 2017 4:30 pm
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Michael, would you will be willing to take on another Standel Hybrid? I have one that needs repaired and I have two extra part chassis'
No one in my area is willing to tackle it. Please let me know. I bought the amp new around 1963 and would be very special to me to have it fixed.
Thanks,
Jerry
rollermusic@cox.net
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http://www.littleoprey.org/ |
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Michael Brebes
From:
Northridge CA
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Posted 5 Apr 2017 9:05 pm
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Yes, I am willing to take on more hybrids. They are not easy to work on. I believe that most of them were from 63 and 64. PM or email me for more details. Let me know the model number of the chassis. This one was a S100V. I have also repaired an Artist that had no vibrato and had 15-18 watts.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Jerry Roller
From:
Van Buren, Arkansas USA
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Posted 5 Apr 2017 11:27 pm
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Michael, mine is a Custom 15 and has black sealed modules. I have two more chassis that have the black modules. I will send you some photos of labels and chassis.
Thanks,
Jerry
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http://www.littleoprey.org/ |
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Michael Brebes
From:
Northridge CA
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Posted 6 Apr 2017 7:26 am
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Yes, please send to my email the pics of all the chassis and their backplates and the symptoms (one channel dead or both, etc.) of each if known.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Brebes
From:
Northridge CA
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Posted 6 Apr 2017 8:29 am
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Just did some research on the internet and, if your amp is an 83L15V Custom 15 combo amp with one 15" speaker, then the schematic is identical to the S100V but the electronics is in a combo style chassis. I have backwards engineered most of the epoxy modules related to this amp.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Michael Lee Allen
From:
Portage Park / Irving Park, Chicago, Illinois
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Posted 6 Apr 2017 12:00 pm
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deleted
Last edited by Michael Lee Allen on 21 May 2018 11:51 am; edited 1 time in total |
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Jim Reynolds
From:
Franklin, Pa 16323
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Posted 7 Apr 2017 2:39 pm
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Michael, what a great job. Your one of a kind, most would never have done it once, let alone volunteer to do it again. These are the electronics I remember when I worked on them, but that was when TV just came out too.
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Zum U-12, Carter SDU-12, Zum Encore, Emmons S-10, Emmons D-10, Nashville 400, Two Peavey Nashville 112, Boss Katana 100, Ibanez DD700, Almost every Lesson Jeff Newman sold. Washburn Special Edition Guitar, Can never have enough, even at 80. 1963 Original Hofner Bass bought in Germany 1963, and a 1973 Framus Bass also bought in Germany 1974. |
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Michael Brebes
From:
Northridge CA
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Posted 16 Dec 2017 10:21 am
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Working on yet another hybrid, a Standel Artist. Got everything working but the Tremolo module which is yet different than any others. It seems that Bob Crook was always experimenting with module design during this hybrid period. Doesn't use a transformer like the Imperial and the module "board" was made up of 4 terminal boards kind of stuck together and using germanium transistors.
The output is feeding something in the blue preamp module. I can't find out what it is attached to without destroying the module. The blue module for the normal channel has been replaced, which is a newer module from the all-solid-state era. It has much more gain than the original one that is in the Tremolo channel, which is either lower hfe transistors or maybe germanium versions.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Nick Stevens
From:
Kentucky, USA
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Posted 16 Jul 2018 10:11 am Standel The Imperial Vibrato
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Michael,
I have recently rebuilt a Standel “The Imperialâ€, Model number S110-V, Serial Number 5258-1. It was pretty trashed and inoperable, and now sounds really nice, except the Vibrato does not work. My understanding is that it is not an uncommon problem. From my research I assumed it was a bad Red Module, since all the other modules, and the entire amp worked. I have deconstructed the Red Module, and eliminated it, and reconstructed the circuit according to my findings, and the several drawings that are available, and all different. I still don’t have Vibrato. My question is, what drawing should I be using. My amp has a Black Module, that appears in only one schematic that I found on the net. From what I can deduce, the Bulb and LDR are in that module. The drawings of the color modules from the Standel site which I have been using, can be a bit confusing. The LDR and Bulb in the Red Module drawing I believe to actually be in the Black Module. But I need help. Attached are the drawings I’ve been using.
#1 Seems to be my amp
#2 Red Module
#3 Vibrato circuit from Later amp?
#4 Black module
Thanks for your time. |
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Jerry Roller
From:
Van Buren, Arkansas USA
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Posted 16 Jul 2018 1:30 pm
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Michael, would you please fix my Standel Custom 15 Hybrid?
Thanks,
Jerry
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http://www.littleoprey.org/ |
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Michael Brebes
From:
Northridge CA
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Posted 16 Jul 2018 4:49 pm
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Nicky, is your Imperial a hybrid or all-transistor? If it is a hybrid, then the schematic is not available online. If it is a later transistor model, then the schematics online should be in the ballpark. Some of these have part of one circuit in one module and the remaining circuitry in another. And yes, the death of the vibrato circuit can be a common occurrence. Finally towards the end, Standel started not potting the vibrato circuits.
Jerry, PM me.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Nick Stevens
From:
Kentucky, USA
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Posted 17 Jul 2018 10:14 am Standel "The Imperial" Vibrato
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Michael,
Thanks for your response. The amp is all sold state, and all wiring and components were exactly as in schematic #1 that I sent you. But here is where I'm confused; the Vibrato foot switch on my amp was connected to the wiper of the Intensity pot, which is not on the drawing of the Red Module and all others. Also, there was not a +32 volt connection on the Intensity pot as shown on the Red Module drawing and all others. It leaves me scratching my head as to what to do? |
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Michael Brebes
From:
Northridge CA
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Posted 17 Jul 2018 12:31 pm
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First, you did not send me a "schematic #1" nor any other schematic.
You need to draw out the wiring around your vibrato module and compare to the overall schematic for your respective amp. Note all differences. Standel was notorious for having overall schematics, and especially module schematics, in constant transition. It is possible that your module is more similar to the hybrid ones. I would highly recommend that you take note of the amplifier model number and find the appropriate overall schematic. If you can't find it, then you will have to do as I do and investigate what is different.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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