Just a few days ago I started a thread on capacitors and resistors, but I figured I should post a new one here since it's a different type of question.

I'm currently in the process of restoring a faulty wurlitzer jukebox, and I've reached the amp.
First of, there are a number of fuses on the list of the manual that don't match with what I find inside the machine, a recurring theme these past few weeks.

In the amp there should be 4 fuses, parts 29, 28 and 27 on the drawing.


29 (first in the image starting from left) : Fuse 2 Ampere slo-blo
in reality : Buss MDL 3 32 Volt

29 (second) : Fuse 2 Ampere slo-blo
in reality : Buss MDL 3 32 Volt

28 (third): Fuse 8 Ampere. manual states Little fuse or bussman MTH (no mention of slow or fast blow)
in reality : 125V Buss GLH 8 (seems to be correct)

27 (fourth): Fuse 15 ampere. Manual states 250V fuse, type ABC.
in reality : 32V Buss AGC 15

Now, the questions I hope you can help me with...


29 (first and second) is referenced as f3 or f4 on the schematic wiring diagram
f3 is on a 36V circuit, f4 I'm not sure... presumably also 36V (I take it this is DC since the fuses haven't popped yet).
However the fuses I find in reality are 32 volt (AC?) and instead of 2 ampere, 3.
I would like to replace these, I have ordered slow blow fuses before so I think these should do the trick:
https://www.mouser.be/ProductDetail/Bussmann-Eaton/BK-MDL-2-R?qs=sGAEpiMZZMtxU2g/1juGqVHgfOhwRYFiDjwt4NgelIw=

28 (third) is referenced as f2 on the schematic wiring diagram
this one's on a 24V loop, I came up with these but I'm unsure to pick a fast or slowblow as replacement
https://www.mouser.be/Circuit-Prote...0x8glZ1yocc4mZ1yycdea&Keyword=8a+125v&FS=True

27 (fourth) f1 on the schematic wiring diagram, is near the power plug.
The 250 V (AC I take it) would seem correct, but the fuse states 32 V so I would like to replace it. How are the ABC vs AGC fuses compared, are they equal in function ?
The closest I could find is this one
https://www.mouser.be/ProductDetail/Bussmann-Eaton/BK-ABC-15-R?qs=sGAEpiMZZMsIz3CjQ1xegR8PufwtdR8uCJUBSNqswmI=

 

While it is good practice to replace fuses with the same type as recommend by the manufacturer – often the information supplied by the manufacturer is limited, as in your situation.

In relation to the voltage rating of fuses, as long as they are rated for at least the voltage present in the circuit they are protecting – the voltage rating will be adequate.

Therefore it is normal to see 250V rated fuses used in lower voltage circuits.

As far as the fuses you might want to replace (other than voltage rating above), you only need consider whether the fuses are time delay (slow blow), or normal (non-time delay).

Fuses that are time delay (slow blow) are prefixed (marked) with the letter T (e.g. T3.15AL250V), whereas normal fuses will be marked prefixed with the letter F (e.g. F3.15AL250V).
The only other requirement is the size (dimensions) of the fuse you are replacing.

There are many other parameters involved in the performance of a fuse – but these need not concern you with the repair of the Wurlitzer.

 

"Fuses that are time delay (slow blow) are prefixed (marked) with the letter T (e.g. T3.15AL250V), whereas normal fuses will be marked prefixed with the letter F (e.g. F3.15AL250V)."

That is not the case with most standard North American fuses. If a part number is matched, the delay time is matched.

You should not use a 32 volt fuse for AC mains operation. They are really "automotive" fuses, though glass cartridge fuses have been obsolete for auto use in NA for a long time. They are still used in low-voltage circuits. F1 should most definitely be rated for the intended AC line voltage.

The MTH and GLH series are both obsolete and the recommended replacement is the AGC series, which is non-delay.

ABC are similar to AGC but in ceramic rather than glass tubes. This gets them higher interrupting current rating - the ceramic tube will survive whereas the glass tube might rupture if very high current is available (as for AC mains). You can find full data for all of these on the web.

Occasionally you will find that a fuse has been replaced with something with a somewhat higher rating. Unless someone is just being reckless, this is usually done because of nuisance blowing - the original rating was too low and blowing would occur without any actual fault in the equipment.

 

For the 15 A 250V I can only find fast blow fuses in the AGC class, ceramic.
https://www.mouser.be/ProductDetail...=sGAEpiMZZMsIz3CjQ1xegR8PufwtdR8uCJUBSNqswmI=

I don't think that is a bad thing considering it is at the start of the electrical loop.

For the 8A (on a 24V loop) I came up with these, for 32VAC. (couldnt find a 125V but I think according to the diagram there's no need for that anyway)
https://www.mouser.be/ProductDetail/576-0311008.H

For the 2A slowblow fuses I have selected these, in both 2A and 3A going by your suggestion the manual might have them stated as too low.
https://www.mouser.be/ProductDetail/504-BK-MDL-2-R
https://www.mouser.be/ProductDetail/504-BK-MDL-3-R