From the Hammond 1750 output transformer series, this is listed as a drop-in replacement for a Fender Vibrolux Tweed, 5F11  -  they're supposed to look similar to the original Fender transformer where possible.  That being said - this sticks out like dog’s balls when mounted on a crusty old amp. 

Materials etc are also supposed to be similar to get as close as they can (within reason I suppose).

It was a bargain, at $76 +GST (Australian dollars) from Mouser, including free delivery.  Like all things Hammond, it feels well made.  

• 8,000 ohms plate to plate
• 16, 8 & 4ohm secondary windings (these options would not have been on the original)
• rated at 15w
• bobbin wound

Turn Ratios

4 ohm turn ratio     44.77  (2004.35)

8 ohm turn ratio     31.58  (997.29)

16 ohm turn ratio   22.38  (500.86)

Frequency response

75hz to 15khz  

Inductance

19.66H

HAMMOND 1751M OUTPUT TRANSFORMER DATASHEET

HAMMOND: 125SE Output Transformer Data

Yes, this is super nerdy and I may be the only person that will ever find it useful - I combined the specs from the Hammond 125SE series into one table, as I found it really annoying to check through individual datasheets.

I recently installed one in a Vox AC4-C1 12 just to see if changing the transformer would improve the amp.  Short story, yes it did.

HAMMOND 125 SERIES, UNIVERSAL SINGLE ENDED OUTPUT TRANSFORMER

A direct link to the table can be found here 

TRANSISTOR, VALVO: OC76 Germanium Transistor Datasheet

VALVO OC76 GERMANIUM TRANSISTOR DATASHEET

TRANSISTOR, VALVO: OC45 / OC44 Germanium Transistor Datasheets

Valvo transistors were produced in Germany, as a subsidiary of Philips (not unlike Mullard in England).   More information on Valvo can be found here.  My experience with Valvo, is that they are pretty much identical to their English counterparts.

The OC45 is a PNP germanium alloy transistor intended as IF amplifier in AM broadcast receivers.

VALVO OC45 / OC44  GERMANIUM TRANSISTOR DATASHEET

TRANSISTOR, GEC: GET Germanium Transistors

GEC is the General Electric Company of England, not the one from the U.S.A.   These are occasionally branded as Mullard.  Full write-up on GEC / GET transistors can be found here

GEC GET 102 - 114 GERMANIUM TRANSISTOR DATA

Type V Max Hfe     P Max (mW) I Max f (Mhz)

GET102     30        100         200                 1000 1.5

GET103     30        55         200                 1000 1

GET104     30        55         200                 1000 1

GET105     40        30         800                 1000 0.9

GET106     15        55         200                 1000 1

GET110     40        20         800                 1000 1

GET111     60        55         200                 1000 1

GET113     15        100         200                 1000 1.5

GET114     15        55         200                 1000 1

TRANSISTOR EQUIVALENTS

Anything from the red colour range from GEC is an audio amplifier; they're listed as being similar to a number of common transistors, such as the AC128.

TRANSISTOR, BRIMAR: AC113 Germanium Transistors

Brimar transistors were made by Thorn and were also commonly branded as Mazda.  A full write-up can be found here

The AC113 is an audio frequency amplifier or driver type germanium transistor.

AC113  GERMANIUM TRANSISTOR DATASHEET

TRANSISTOR EQUIVALENTS

Being a fairly generic audio amplifier, they're listed as being similar to a number of common amplifier transistors, such as the AC125.

WHAT ARE THEY REALLY LIKE?

Testing results from a lot of 10:  The range of gain and leakage is huge - from 45hfe with very little leakage, right up to 330hfe with a lot of leakage.  Several were a bit over a 100hfe with moderate leakage.  One was dead, only useful as a diode.

So if you see some going cheap and are tempted to grab a few, buy more than you think you will need, as there will most likely be wastage.

TRANSISTORS: Soviet Germanium Transistor Data

Germanium transistors from the former USSR are cheap, generally high quality, available in large quantities and very cheap compared to their European counterparts.   

They are their own thing and are not direct copies of European transistors - you can find similar transistors, but they are never like-for-like replacements.  They nearly always sound different and have their own character.  So when sellers on eBay compare the Soviet version to a western one, just use this as a rough guide.   

Note:

• Check pinouts, as B, C, E is common
• The emitter is often marked with a dot on the case
• The case is sometimes connected to the base
• hfe on most datasheets will be on the high side, due to high test currents.  Look at the minimum gain as a more likely average than the maximum
• They tend to be low leakage compared to European transistors, which means that many will not work in circuits that require high leakage to self-bias 

SOVIET-ERA GERMANIUM TRANSISTOR DATASHEET

Link to the spreadsheet

SUPPORTING INFORMATION ON SOVIET TRANSISTORS

Soviet transistor pinouts

Soviet numbering system

Discussion on DIY Stompboxes

TRANSISTORS: Mullard Data Book 1965 - 66 & 1974 - 75 Excerpts

Transistor datasheets from Mullard for;

Germanium:    OC44, OC45, OC70, OC71, OC72, OC74, OC75, OC78, OC81 and OC81D

Germanium:    AC126, AC127, AC128, AC176, AC187, AC188

Silicon:            BC107, BC108, BC109, BC186, BC187

MULLARD DATA BOOK 1965 - 66

MULLARD DATA BOOK 1974 - 75