AC15CC1 opinion on PT

[mresistor]

I have an ACC15CC1 here with a blown PT, secondary internal short.  The options for replacement are slim pickens and expensive.  One is from the EU at Tube Amp Doctor and will run around $175 plus any fees crossing the US border.   The other is around $250 from Mercury Magnetics.    They are both nice and one is rated at 150ma the other (mercury) is probably also but I don't know for sure.


There is another option though. A Hammond 290CZ. The problem with it is that the mounting specs are too small for the chassis. It could be installed with a little ingenuity. The second problem is it is only 120ma. Third the secondary HV is 15VAC higher than TAD PT and the mercury PT I don't know.


This amp appears to have voltage dropping resistors on the HV secondary of 82 ohms 5W.  I guess the voltage dropping resistors could be changed to drop more AC volts to get the EL84 plate voltage down to a more reasonable level. 


Do you think the Hammond is worth messing with?

[Latole]

This one ?
https://www.partsisparts.net/category/catalog/vox-amp-parts/vox-transformers?page=2

[mresistor]

Thank you Latole.. that is interesting   It appears to have 8 wires and the CC has 9 wires.  But who knows..  I emailed them earlier because they had the original AC15CC1 PT but show it as discontinued. and the answer to all my questions was "Sorry I can't help you".   It does look like the AC15C1 has the 25V winding too.  I asked Korg seller on Reverb if that one you show will work. 
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[Latole]

......and the answer to all my questions was "Sorry I can't help you". 

No the answer, is sorry I have to much work to work in you amp

[mresistor]

No the answer, is sorry I have to much work to work in you amp

what work?  Are you being sarcastic?   


It appears the PT you have pointed out to me has 6 secondary wires. Two each of yellow red and orange.  It's for the new model of which they only supply the schematic to authorized repair centers.
To me that would indicate a non center tapped HV winding for use  with a bridge rectifier, which would be totally incompatible for the AC15CC1 amp.


So  I am back to the choice of the Hammond or the Mercury Magnetics.  The MM is drop-in and probably rated higher more like 150ma.

[66Strat]

Plate current and screen grid current draw at maximum signal for two el84 tubes in push/pull operation are 2x46 (92)  ma and 2x11 (22) ma respectively for a total maximum current draw of 103 ma. Add in 4 ma for the pre-amp and PI tubes lands you at 107 ma total maximum current draw. This is well within the 120 ma rating of the Hammond transformer.

The 68 ohm resistors preceding the diodes in power supply are there to approximate the voltage drop of a tube rectifier. You can experiment with the values here too get the rectified DC voltage that you want.

Hammond has other transformers that may suit your needs. Likely candidates include the 290PAZ in a lay down transformer or the 272BX in a stand up transformer.

[tubeswell]

(92)  ma and … (22) ma total … 103 114 ma. Add in 4 ma for the pre-amp and PI tubes lands you at 107 118

Fixed

[mresistor]

(92)  ma and … (22) ma total … 103 114 ma. Add in 4 ma for the pre-amp and PI tubes lands you at 107 118

Fixed

So that is very close to maximum, a little close for my comfort level.   I'm going to ask MM what the specs are for their replacement. 


I found one other hammond PT that has a 25V winding  and it also had a non-center tapped HV tap.

[66Strat]

(92)  ma and … (22) ma total … 103 114 ma. Add in 4 ma for the pre-amp and PI tubes lands you at 107 118

Fixed

D'oh

(92)  ma and … (22) ma total … 103 114 ma. Add in 4 ma for the pre-amp and PI tubes lands you at 107 118

Fixed

So that is very close to maximum, a little close for my comfort level.   I'm going to ask MM what the specs are for their replacement. 

The transformer is rated to deliver 600 VCT under a 120 ma load. That is not the maximum rating. Likewise, the 290PAZ is rated to deliver 580 VCT under a 140 ma load.

MM makes nice transformers. It would be interesting to see how they compare.

[tubeswell]

Yes I think 120mA rating is okay

[mresistor]

66Strat  - I think you are overlooking the fact that this AC15CC1 has a 25 VAC secondary winding of the PT..  It powers that reverb and trem digitalcircuitry.

[66Strat]

I missed the 25 volt winding in the schematic. I mistook the 25 VAC winding for the heater winding. Regardless, the 290CZ has the requisite 25VAC winding and sufficient current capacity for the HT winding, if you choose to use it. The only downside that I can see is fitment. A sheet of .090 aluminum would fix that problem.

As I said before MM makes nice transformers. It would be interesting to see their specifications and cost.

[mresistor]

Thanks 66   not a problem  cost is a factor for the guy though..   

[kagliostro]

.... It would be interesting to see their specifications and cost.

The other is around $250 from Mercury Magnetics.

May be a MM OT worth the effort (may be, but not sure), but as PT one with compatible spec will be enough, despite all Hammond is a good brand

Franco

[mresistor]

I said this above
It appears the PT you Latole pointed out to me has 6 secondary wires. Two each of yellow red and orange.  It's for the new model of which they only supply the schematic to authorized repair centers.
To me that would indicate a non center tapped HV winding for use  with a bridge rectifier, which would be totally incompatible for the AC15CC1 amp.


However upon closer look at the photo of that PT it does have 7 total secondary wires..   the extra short white wire was fooling me.   

[kagliostro]

In doubt ask to the seller, often photo are only an example and didn't exactly correspond to the item


Franco

[mresistor]

In doubt ask to the seller, often photo are only an example and didn't exactly correspond to the item
Franco

Thanks Franko   there are other places where that PT is for sale and it appears the same.  I talked to Vox USA and they just said it wasn't a suitable replacement, and of course they will not release the schematic or any specifications. But I'm confident that PT would work except the mounting dimensions may not be correct. 


I'm going to use a Hammond 290CZ.  At least I know 100% what I'm getting.