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Univox Bass Amp Model# U-1235

#3
I see that it has 2 6L6 tubes but also claims to have a solid state power amp section...

How many watts is it?

I found it buried at my parents house, looks like it is going to need some work to get it back up and running. Is it worth restoring or would it be a waste of money?
 
#4
It has a solid state power supply. And it will do probably 40-45w.

They had a sticker on them claiming "100w", but that is peak power - on a good day.
I doubt the power supply would be able to do that - the one in mine is rather wimpy.

Well, it all depends on how much it needs, if it needs $50 to $150 of work, i'd say go for it. Otherwise, not so much.
 
#5
Hi, I recently began investigating an old amp head that was here at my house when I bought it. Looks like this......
026.jpg


First I thought it was the U-1235. Found this info on it.....

U1235.jpg

''U-1235 Bass Amp System (1, 2, 3 4) - 5 tubes (2 6L6, 2 12AU7, 12AX7) and solid state power supply, 50W, 3 inputs (bass, high, low) w/ deep and sharp selector switches, , 2x12 cabinets with Eminence special design speakers. Controls: volume, bass, treble. Apparently there was a guitar version made too, the only known difference was that it had reverb and tremolo. Speaker cab are rear loaded and is not ported. It has matching red and black dot in the center. The dimensions are 30 1/2" High x 22 1/2" Across and 13 1/2" Deep. There are two handles located on the sides and a single input on the back. Also know as the E-3."

Then , upon further research, I came across the Univox 1968 Catalogue. An item in the search has a peace by a fella who had just bought what appears to be the U-235 PB, listed in the catalogue.

'This is a nice vintage 1960s Univox tube amp head. This is actually a bass amp but is probably better suited as a guitar amp today. The tube line-up is two 6L6 power tubes and three 12AU7 tubes. It was made is Japan. T is an online Univox website that has a scan of the 1968 Univox catalog. It has what appears to be the exact same amp identified as a model U-235 PB. The catalog describes it as a 70 watt amp. The front control panel features 3 inputs (BASS, HIGH and LOW), 2 tone switches (DEEP and SHARP), Treble, Bass and Volume controls, a red power light, fuse cap and 3 way On/Off/Standby switch '





With this photo....

U-235PB.jpg


Still not sure if I have the U1235 or the U235, but it's gonna be fun finding out!
 
#6
Mogpipe, from what I found out the U-1235 is the head and a cabinet. Not sure if it is the 212 cab or not. Mine has a 15" cabinet. The head by itself is the U-1236. No idea on the logic behind that numbering system..

So I cleaned up the tolex last night and decided to plug it in and see what was in store for me. Amazingly it works, and I noticed that the 6l6's are not original as they are now Groove Tubes. All the switches and pots crackle, but I expected that. It definitely has a hum coming from it. But like I said, at least it works.

Kramer, from your post is it safe to assume that you are an experienced tech?
If so how much would you say it would cost to have a grounded three prong cord installed as this one is only a non-grounded two prong. And with a grounded cord installed will that help eliminate the hum?
 
#8
I owned one for a short while. Good amp, not too much power for bass, more like a bed room amp or a small guitar head for blues kind of players. I used it as a backup to my b15n (not that i needed one but i got it cheap and mint condition). Fat round tone for bass and the switches made it pretty easy to find a miriad of tones. I had one of my friends try it on guitar and he hooked it up to a 4 12 marshall and it pretty much had a good clean tone typical of early tube amps... Again don't expect a lot of power from it, even as a guitar amp.

Sorry for the old crappy cellphone pics.

IMG00515.jpg

IMG00513.jpg

IMG00522.jpg

IMG00518.jpg
 
#9
KramerBassFan said:
It has a solid state power supply. And it will do probably 40-45w.

They had a sticker on them claiming "100w", but that is peak power - on a good day.
I doubt the power supply would be able to do that - the one in mine is rather wimpy.

Well, it all depends on how much it needs, if it needs $50 to $150 of work, i'd say go for it. Otherwise, not so much.
Click to expand...

Its powered by two 6l6s for the power section, its a tube amp.
 
#12
T.A.P Bass said:
Kramer, from your post is it safe to assume that you are an experienced tech?
If so how much would you say it would cost to have a grounded three prong cord installed as this one is only a non-grounded two prong. And with a grounded cord installed will that help eliminate the hum?
Click to expand...

Experienced tech? I dont know if i'd go that far... ;)

I have done the 3 prong mod before (Ampeg V4) and its not hard if you know what your doing. But i'd imagine that it would take less than an hour total for a competent tech on this amp. These Amps are not very complex at all.
It could help eliminate some of the hum, but its hard to say for sure.

Garmenteros, what exactly are you asking?
 
#13
I was asking if amps with solid state rectifiers are more reliable than amps with tube rectifiers... if I recall correctly the main issue with early musicman hd heads was that the tube rectifier gave out quite often and later models had it replaced by a solid state rectifier. I'm sure others who've owned amps can confirm or clear this up for me... Then again doesn't my b15n have a 5ar4 tube rectifier and I've never had any issues with it besides scratchy pots and the occasional hum due to unstable voltage...
 
#14
I don't personally know about the reliability factor, (never had anything with tube rectification) but you do need a good amount of tube rectification the bigger the amp gets.

With the MM heads, i'd imagine the switch was due to the large price difference - a few diodes vs. a tube.

EDIT: now that i think about it, I worked on a friends MM HD130 and it was SS recti, but had a 12ax7 as its phase inverter, and later got a SS PI.

Are you sure you aren't thinking of this?
 
#16
Just checking out info for this amp head and noticed somebody mentioned getting rid of the 60Hz hum.

Here's how to do it. You have to replace all of the electrolytic capacitors, starting with what might be the main culprit......the rectifier filter. In the Univox U-1236 I have there are 4 electrolytics: the filter capacitor (the big one) which is a 50/50 microfarad 350 volt canister capacitor. The one next to it is 50 microfarad 150 volt capacitor, the third one is a 20 microfarad 350 volt capacitor and the last is a 10 microfarad 350 volt capacitor. THESE ARE ALL ELECTROLYTIC CAPACITORS.

Just some basic things to keep in mind when re caping an amp.........

1. Make a ground discharge rod...a screwdriver with an insulated handle and an alligator clamp wire to discharge all electrolytic capacitors. They can hold a charge (that can change your way of thinking) up to several days.

2. All electrolytic capacitors have a polarity....positive and negative and must be installed observing the correct polarity.

3. When choosing capacitors, make sure you choose ones that meet or exceed the microfarad and voltage rating of the ones you are replacing.....never go smaller!!!! Try to stay close to the original parts specs as you can. You could go bigger, but it may or may not cause small problems although you will notice that the bigger you go the more expensive it is.
 

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