AMI amplifier assembly for F,G,H, or I jukeboxes

[greenmartian]

I am repairing an AMI H-100 and need to find a rebuilt R-145 amp or have the amp I have rebuilt.  It current amp blows the 2 amp fuse immediately when plugged in with no tubes or connections to it. Therefore, I suspect the transformer is shorted and needs replaced. Can anyone direct me to a source for either a replacement amp or a technician to repair my current amp? I believe this amp was used in the models F, G, H, and I with 80, 100, or 120 selections. Any and all help would be appreciated!
Thanks... Marty

[greenmartian]

Does anyone know where I can find a rebuilt r145 amplifier or someone to rebuild one?
Marty

[jukeboxmarty]

You apparently asked this question two days ago when you started a thread in the 'parts wanted' forum.

Since we don't need two threads asking the same question... which one should be deleted?

[greenmartian]

You can delete both of them if you prefer. There has been few reads and only your response correcting my actions.  Being new to the forum, I thought I had posted the thread improperly the first time when I posted it as 'general'. I believed I should have posted it under 'AMI/Rowe' instead.  Therefore, I did so.

[jukeboxmarty]

No, not *really* looking to delete anything, but I will combine into one post.

Carry on...

[jukeboxmarty]

Aug 9, 2023 0:12:49 GMT greenmartian said:

It current amp blows the 2 amp fuse immediately when plugged in with no tubes or connections to it. Therefore, I suspect the transformer is shorted and needs replaced.

I believe your assessment is probably correct... shorted transformer.

You may have to be patient on this particular item. Parts machines do not come up very often, and I doubt most amp rebuilders would have this transformer laying around.

I would continuously check eBay. There isn't anything now but there are several earlier model amps available. I don't know anyone who deals in AMI parts.

-(also) Marty

[jukenorman]

You could replace the transformer with a Hammond, manufactured in Canada, if you were up for that!

Norman.

[greenmartian]

Thanks for both replies.  I have been watching Ebay and contacting jukebox sources I know of and will continue to do so.  The box was a train wreck in most regards and it is unlikely it will be ready to play anytime in the near future. I can wait.  Does Hammond produce transformers as replicas for existing boxes or are they generic and to be modified to match the desired windings/voltage outputs to fit the application requirements?

Thanks for your patience with a new member to the forum.
Marty

[jukenorman]

Hammond produces transformers primarily for guitar amplifiers, but you'll definitely find transformers that are electrically identical to yours (no modifications required). Hammond is always my personal preference because buying a sixty odd year old original transformer - well, you have no idea of its history or where it's been stored etc! You might have to make a minor modification on the physical mountings but that's not usually much of hindrance. My AMi Continental amp has a Hanmmond mains transformer fitted.

There is a company in Italy that has started making jukebox transformers that are totally identical to the originals but not your one as yet.

Norman

[greenmartian]

Many thanks Norman.... I have contacted Hammond concerning my transformer need and hope to hear back from them soon!

[jukenorman]

Just in case you don't get a helpful reply from Hammond, there's a fairly simple way to size the transformer electrically. In your case there are three secondary windings - 350VAC centre tapped for the HT (B+), 5VAC for the 5U4 heater and 6.3VAC for the heaters on the other tubes. So check the data sheets for the tubes and add up the heater currents (except the 5U4 which has its own winding) and then go for a transformer just over that heater current. Don't be tempted to oversize the heater current because that will tend to reduce the life of the tubes.

Norman.

[greenmartian]

You must have known from my messages that I am not trained in reading electrical schematics to be able to determine the exact transformer I need for the H100. Many THANKS for the additional information! I checked the data sheets for each of the additional 5 tubes and got the 'heater currents' as 2 6L6's, each at .9 amps for 6.3v, is 1.8 amps; 2 12AU7's, each at .3 amps for 6.3v, is .6 amps, and a 12UX7 at .3 amps for 6.3v. This would equal a total 'heater current' of 2.7 amperes. Is that correct?

Pardon my ignorance, but this would equate to my needing an output transformer from Hammond with a primary winding of 350 VAC, two secondary windings of 6.3 VAC and 5 VAC each, and a current amperage of greater than 2.7 amps? Maybe 3 amps?

In my amateur amplifier rebuilds, I have never had to replace a transformer where I couldn't find an exact transformer from another amplifier to fill my need. All I had to do was identify the primary and secondary windings. This is a first for me and, if all goes well, a preferrable way to rebuild. Your assistance is greatly appreciated!!!
Marty

[cedric]

Hi,

As Norman say (hello Norman ) Piemme Elektra makes output and power transformer for jukebox. For the R145, I think you can find the 2.
Have a nice day, night...

[jukenorman]

Hi Marty,
You want a transformer with primary windings around 120VAC and three secondary windings. At this point, I'm going to suggest waiting to see what Hammond reply. I also need to add that I made a bit of a schoolboy error above and what you actually require as the centre tapped winding for the HT (B+) is around 600VAC to maybe 700VAC.  The Hammond 372DX is probably a good option (600VAC CT).

As Cedric says, the Italian Piemme Ekekra range does have an exact replica but I'm not sure if they are available in the US and shipping from Europe will no doubt be pricey but you can see what is available here at Jukebox Revival in the Netherlands
www.jukebox-revival.eu/en/products/transformers-4925/piemme-elektra-transformers-5418
You require the power transformer for the R145.


Norman.

[tvtechrich]

Before you replace the transformer, try it without the tubes, a shorted tube will also blow fuses.