Restoring the Jimi Hendrix Univibe

[Frantone]

In 2001 I had the very rare opportunity to restore one of Jimi Hendrix's toured Univibes - a true piece of history!

The unit had not functioned for years but the owner wanted it to be operational again.  It had some interesting modifications to the circuit board.  One interesting feature was that the screw- down opto shroud had been replaced with a duct tape covered RCA Vacuum tube box top which had been adhered to the PCB with white glue.  Why I have no idea, but it may have increased response because it was larger than the original shroud and perhaps because it was made of white cardboard it diffused the light better.   

So you may be asking yourself if I played the pedal after the restoration was complete?   I did.    The pedal had so much mojo it brought tears to my eyes!  What a sound - and words fail to describe such a thing.

Anyway, I thought I would share this one with you EEVBloggers this weekend - ENJOY! 

[SeanB]

What was wrong with it other than just poor connections? +10 for the showing of it.

[Frantone]

There was surprisingly little wrong with it considering the mileage - It needed the ubiquitous recapping and the opto bulb needed replacing.  Most of the work involved repairing the mechanical parts of the foot controller and interconnects. 

[SeanB]

Always the same parts that fail, transistors got very reliable very early on in their development, and have remained so basically since then. Same with film capacitors and those carbon composition resistors that would drift, go noisy  and otherwise misbehave but keep on working. Still have a box of them around, and still use them when I want to have a nice old style resistor in a non critical application.

Looks like that unit was made mostly with good quality Japanese made transistors and capacitors.

[Frantone]

It was well designed and very rugged for it's time - Most effects pedals of that era were filled with parts made of wood and tin foil kinda strung together.   

[Biff383]

Thanks

[jucole]

Ever since I heard "Machine Gun" on the "Band of Gypsys" album i've always wanted one of these!

[Frantone]

The owner of the Univibe had gotten the pedal from Hendrix himself - so to speak.  He was a teenager living in NYC early in 1970 and was in Manny's Music in Midtown when Hendrix came in with a box of gear he wanted to sell to the store.   When Hendrix left, the guy went to the clerk and said he wanted to buy one of the things  Hendrix had dropped off, and the clerk said sure - there were three Univibes in the box, two of which did not work, and this one did so cash was handed over and he got his Hendrix Univibe.  Hendrix had a studio in New York that was in trouble financially, so this seems to be part of that time.

[mamalala]

Don't get me wrong, but i think one of the main reason such (old) effects are "heavenly" is because of their simplicity and less-than-average wiring. I have seen a lot of the modern units, with convoluted circuits, cabling done extremely nice, etc. But you never get the crackle & vibe that you get with these old units. I'm pretty sure the reason is _not_ because we nowdays can produce more stable resistors, or have better processes to produce transistors....

Greetings,

Chris

P.S.: It's always an extremely satisfactory thing to show these things to audiophools. After all, what they listen to is actually generated by these things. What good is a 4k+ power supply cable if you look at what these olden day effect circuits do....

[ivan747]

I always wanted to come up with a novel distortion pedal. Two year on and I still get ear-bleeding sound when playing a single note. You don't even want to hear a chord 

[mamalala]

I always wanted to come up with a novel distortion pedal. Two year on and I still get ear-bleeding sound when playing a single note. You don't even want to hear a chord 

Hint: Many tubes work just fine with a rather "low" voltage. Stuff like 24 volts is OK for a lot of triodes. Easy to generate as well, considering that you don't need much current. Of course the filaments are alwas a huge power hog...

As for transistors or FET's, try to drive them so that "just somewhat below" full conduction results in full gain. FET's are somewhae better for this, since their characteristics are more tube-like. Another thing is to use a rather hig impedance suppy/bias source compared to the signal. This will cause additional distortion since the supply will break down in voltage at higher spikes....

Avoid high capacity for the supply, you surely do not want it _that_ stable. In general, tend to design it towards the "owrst case possible" regarding that stuff, instead of things like "really stable supply!". Keep in mind that the 9V batteries usually used in pedals are rather high impedance and low cacaity.

Greetings,

Chris

[Quick5pnt0]

I don't have much to add other than to say how awesome it is that you got the chance to handle something like that from the great Hendrix!

[Frantone]

Don't get me wrong, but i think one of the main reason such (old) effects are "heavenly" is because of their simplicity and less-than-average wiring. I have seen a lot of the modern units, with convoluted circuits, cabling done extremely nice, etc. But you never get the crackle & vibe that you get with these old units. I'm pretty sure the reason is _not_ because we nowdays can produce more stable resistors, or have better processes to produce transistors....

I don't subscribe to the idea that old pedals sound heavenly by default - but this Univibe certainly did - and for may reasons.  One being that I had restored it to proper function (which is seldom the case with vintage pedals) and it is a very good stable design.  That cannot be said of most other commercially made effects of the 1960's. 

[Frantone]

For contrast - here is a pedal that Manny's Music actually made themselves and sold in the early 1970's - Manny's Fuzz.  I restored this pedal in 2002.  It is more common for its time.   

[rama claproth]

UniVibe owned by Jimi!!! WOW that's so HOLY!!! Thank you for posting this!

BTW I notice there is a capacitor under the board, what is the value of the cap? Is it in parallel together with the 15nF?

[Frantone]

BTW I notice there is a capacitor under the board, what is the value of the cap? Is it in parallel together with the 15nF?

It is a .005uf ceramic original 'bodge' in the feedback loop of one transistor.  Not uncommon for RF issues.

[Frantone]

Always the same parts that fail, transistors got very reliable very early on in their development, and have remained so basically since then. Same with film capacitors and those carbon composition resistors that would drift, go noisy  and otherwise misbehave but keep on working. Still have a box of them around, and still use them when I want to have a nice old style resistor in a non critical application.

Looks like that unit was made mostly with good quality Japanese made transistors and capacitors.

It is true - even the earliest silicon transistors drift relatively little over time, and if the circuit is properly balanced usually need no rebiasing.

[SeanB]

My PC amplifier is a 1070's vintage National Panasonic quad control centre, mostly used as volume control and input switching. Only thing I did to it was to replace the power lamp with a LED, and to replace almost all of the electrolytic capacitors in it, as they were getting iffy. Still has the original PNP transistors, even though they are using a RF mixer transistor, probably as it was a device with a guaranteed low noise figure. Made the power supply a lot bigger capacitor wise, from 100uF to 2200uF, it will run for over a minute on power off before it starts to distort the output at under 3v supply from the normal 30V.

[Radio Tech]

That makes my heart pound when I see folks restore old stuff like this, very exciting. Especially when it has a legend attached to it. It is very cool of you to share this. You Rock!!

75 percent of the repairs I do here in my shop are tube related equipment.  And the rest are early solid state equipment. Some with over 3500 volts on the plates, which will zap you a good one.
 I just finished a 1954 National NC-98 receiver.  That was fun. No paint job just restored the functions of it. Was so excited with it I had to post it on an old radio forum I am a member of.

[Frantone]

Over the past 20 years I have resorted a lot of antiques - in the '90's I had a part time antique radio repair and resto business, and after I got to NYC in '98 I was sought by local artists to restore vintage pedals.  Tubes?  You betcha.  Just look at my blog!

[Radio Tech]

Sounds cool, I look it up. Thanks again for sharing.

[rama claproth]

BTW I notice there is a capacitor under the board, what is the value of the cap? Is it in parallel together with the 15nF?

It is a .005uf ceramic original 'bodge' in the feedback loop of one transistor.  Not uncommon for RF issues.

RF you mean as radio frequencies? I never notice the Univibe pickup radio signals like the Fuzz Face. Correct if I'm wrong but looks like the cap under the board is joined with the 15nF if I'm not mistaken, which it does connects with the middle leg of the transistor and the 4K7 resistor.

Thanks for the reply Fran

[Frantone]

RF you mean as radio frequencies? I never notice the Univibe pickup radio signals like the Fuzz Face. Correct if I'm wrong but looks like the cap under the board is joined with the 15nF if I'm not mistaken, which it does connects with the middle leg of the transistor and the 4K7 resistor.

It is a bodge that is not uncommon.  High gain transistor or op amp stages can oscillate at high frequency and the cap is in there to stop this by creating filtered feedback.  You wouldn't pick up detected audio from local radio signals, per se.

[rama claproth]

RF you mean as radio frequencies? I never notice the Univibe pickup radio signals like the Fuzz Face. Correct if I'm wrong but looks like the cap under the board is joined with the 15nF if I'm not mistaken, which it does connects with the middle leg of the transistor and the 4K7 resistor.

It is a bodge that is not uncommon.  High gain transistor or op amp stages can oscillate at high frequency and the cap is in there to stop this by creating filtered feedback.  You wouldn't pick up detected audio from local radio signals, per se.

Hmmm got it. I notice the footage from the Isle of Wight, Jimi was having trouble with radio frequencies and he stopped using the UniVibe during the show and all went okay. So the radio frequencies must be coming from the UniVibe because he kept on using the Fuzz Face with no trouble. So it could be on that show his UniVibe didn't had that cap. Aha! Thanks for the info Fran        

[Frantone]

Here is a capper for this thread - my bodging/mod of a vintage late 1960's British made WEM Copy Cat tape delay.  Notice the tack soldered resistors and a heat sink for one of the original germanium transistors (yes, it got hot!).  New electrolytics - can't help that.  A very bad design to begin with, and very poorly soldered over all, but I kept it as original as possible with some minor mods to reduce noise.