Univox Model???

[plexi50]

I got this earlier today and am trying to figure out the model number. I cant go by the tubes in it because i do not know if they are correct tubes. The amp has Tremelo. (1) 9 Pin Socket. (3) 7 Pin Sockets. 12AX7 - 6AV6 - Empty - 6202/6X4 Rectifier. I figure 8 watts. Serial # 1623. Info?

[plexi50]

Pic

[PRR]

Possible: UNIVOX U45B
https://el34world.com/charts/Schematics/files/Univox/Univox_tube.pdf    Page 14
Large grains of salt needed.

It's got the three input resistors so you and two buddies can play at once. Not the same value as in your amp but this is not government work. It has the trem ("trim"?). No power rectifier shown. The 1.7K and 2K power chain resistors seem very unlikely (8 Watts waste heat??); assume higher values. 

Ah: maybe U45(no B):
https://el34world.com/charts/Schematics/files/Univox/Univox_u45.pdf
Univox was a brand for ACA, an old-school amp maker (literally: school PA amps from 1935) but in this period they moved production from the Hudson River to a Japanese operation and I think assembly in SE Asia. So documentation was less important than cranking iron to stores.

[plexi50]

Possible: UNIVOX U45B
https://el34world.com/charts/Schematics/files/Univox/Univox_tube.pdf    Page 14
Large grains of salt needed.

It's got the three input resistors so you and two buddies can play at once. Not the same value as in your amp but this is not government work. It has the trem ("trim"?). No power rectifier shown. The 1.7K and 2K power chain resistors seem very unlikely (8 Watts waste heat??); assume higher values.

The U42 shows tubes / 12AX7 - 6AV6 - 6AQ5 - 6XW

[plexi50]

I think your  right PRR on it being a U45B. I have only (1) 6BM8 tube. I have the others. Let me dig in the garage in some tube cases i have for another 6BM8. This amps cab matches the dimensions and black cloth with silver specks in it of the U45-B

[tubeswell]

Trace the circuit connections to the 7-pin sockets- should be able to reverse-guess the type of tube from examining the heater, high-voltage (plate and screen), low-voltage (cathode) and grid pin connections. Any compatible 7-pin tube should be a safe bet.

[plexi50]

I have some NOS GE 7199 tubes. Checking the pin out now. It looks? Nope!

[plexi50]

Possible: UNIVOX U45B
https://el34world.com/charts/Schematics/files/Univox/Univox_tube.pdf    Page 14
Large grains of salt needed.

It's got the three input resistors so you and two buddies can play at once. Not the same value as in your amp but this is not government work. It has the trem ("trim"?). No power rectifier shown. The 1.7K and 2K power chain resistors seem very unlikely (8 Watts waste heat??); assume higher values. 

Ah: maybe U45(no B):
https://el34world.com/charts/Schematics/files/Univox/Univox_u45.pdf
Univox was a brand for ACA, an old-school amp maker (literally: school PA amps from 1935) but in this period they moved production from the Hudson River to a Japanese operation and I think assembly in SE Asia. So documentation was less important than cranking iron to stores.

Ok U45 no B. I have all those tubes and it looks right. More eye work to do!

[plexi50]

Working and sounds nice.  Tremelo is working good. (1)12AX7 - (1) 6AV6- (1) 6AQ5A - (1) 6X4.
Plate 248vdc / Screen - 237vdc - Cathode +10.98
So a U45 no B!

[astronomicum]

It appears to me that the tube numbers are stamped on the chassis. Earlier years had the tube numbers painted on the chassis. Based on the terminal strip construction, I would say an early model U45 due to the stamped numbering. I can see that it has a trem switch on the speed pot. Does it have NFB?

[plexi50]

It appears to me that the tube numbers are stamped on the chassis. Earlier years had the tube numbers painted on the chassis. Based on the terminal strip construction, I would say an early model U45 due to the stamped numbering. I can see that it has a trem switch on the speed pot. Does it have NFB?

Not on the schematic. Eyes are straining tonight to trace wires and resistors. From what i see all the resistor values follow the U45-B schematic.
I will confirm more tomorrow. Voltages as well within a volt or two on the U45 schematic.

[astronomicum]

Not on the schematic. Eyes are straining tonight to trace wires and resistors. From what i see all the resistors follow the U45 schematic.
I will confirm more tomorrow. Yes the entire amp follows the U45 Schematic resistors. Whoopie! Voltages as well within a volt or two.

The second page of the schematic shows NFB in red with a question mark. Curious as to the feedback resistor value if it has NFB. I have found that later models U45B added NFB even though that is not on the schematic either. No biggy. Don't trouble yourself.

[Platefire]

Well you got it going fast! Looks like it has a good quality Alnico Jensen 10"(?)Speaker

[plexi50]

It sounds pretty good! Jensen speaker 220433. P12S-C7909

[bmccowan]

Nice! Agree that it is not a B model. I have one and its a 2x6BM8 amp. I have another 2x6AQ5 Univox for which I have not determined a model #. Apparently there are many undocumented Univox amps. Parts bin amps if you will.
Both my amps hum more than I want. Even after teaching them the words. I attribute it to the less than ideal placement of the OT in relation to the PT. If yours hums after replacing filter caps, that is likely the culprit based on many posts I've seen. It looks like there would be room to rotate the OT 90 degrees. No such room in the U45B which has a PCB taking up all the available space.

[isaac_teller]

https://el34world.com/charts/Schematics/files/Univox/Univox_U75.pdf

[plexi50]

Univox schematics and info is definitely among the hardest to find. I was surprised after checking the heater filament leads as tubeswell suggested that it all became clear immediately. All the 220K / 390 /470K resistors made it clear it was a U45. I love low wattage amps!When i look back at all the Marshall amps and cab stacks i had i wonder why? It was a phase i think we all go through. Every amp has it's place in the world of tone. I love the Gibson G20 & G30 amps. And the Gibson Country Western amp.

[plexi50]

https://el34world.com/charts/Schematics/files/Univox/Univox_U75.pdf

Nice and readable! This morning i'm on a Univox mission to find all the info i can. Lucky i had that NOS GE 6AQ5A. My NOS supply is getting thin. These are the last of the 12AY7 tubes i have.Their already set to go into a Fender Super V Front. 1992 Model.

[bmccowan]

https://el34world.com/charts/Schematics/files/Univox/Univox_U75.pdf

Nice and readable! This morning i'm on a Univox mission to find all the info i can.Lucky i had that NOS GE 6AQ5A. My NOS supply is getting thin. These are the last of the 12AY7 tubes i have.Their already set to go into a Fender Super V Front. 1992 Model.

Thanks for posting the U75 - I'm pretty sure that matches the circuit in my 2x6AQ5 Univox - but it seems the U75 was a 2x10 amp and mine is a single alnico 12" Jensen (no complaints there.)
I also have run out of NOS 12AY7 and have found the JJ 5751 to be a reasonable alternative.

[astronomicum]

Thanks for posting the U75 - I'm pretty sure that matches the circuit in my 2x6AQ5 Univox - but it seems the U75 was a 2x10 amp and mine is a single alnico 12" Jensen (no complaints there.)

There were four models of 2x6AQ5 Univox Amps that I am aware (one of them being a Lafayette brand); U75, U80, U102, U155r. With a single 12", it may be a U102. The U102 had four controls and a 6AU6 in the V1 position.

[bmccowan]

Thanks Astro - I'll take a look. I bought it a long time ago and if I documented it, I forgot where I filed it.