Performer/Roc-pro transformer

[Vitrolin]

hey

Got a fender performer 1000, mains transformer blown.
From the schematic i can see secondaries 60VAC center tapped or 2x30VAC, but what would the current rating be?
The chassis says 300W but that seems excessive, any thoughts?


http://support.fender.com/schematics/guitar_amplifiers/Roc_Pro_1000_schematic.pdf

[Enzo]

The second page of the schematic shows the power transformers.  Where are you?  120v land or 240v land?  The part numbers for each are printed there.

In either case, did you check with Fender to see if they still have them, and if the part number has changed since the drawing?  if they have them, then you can order the exact part from any Fender dealer or supplier.

300 watts from the mains for a 100 watt amplifier doesn't sound excessive to me, they are not 100% efficient.

[Vitrolin]

i know they are far from 100% efficient but i often seen somewhere 150-200W for 100W out but then again the heater supply dissipates about 7W
i'm in 230 land there are suppliers that offer a replacement but the price is way too high 135 euros plus shipping so i was going for an alternative.
a toroidal equivalent cost about half, but then i would have use a different fuse due to increased inrush maybe a time-lag same rating would do...

[Enzo]

Rather than fight the fuses, use a normal fuse rating but add a series inrush limiting thermistor in the mains lead, like so many other Fender amps.   In fact, I see there is already one in your amp, it is on the schematic page lower center

[Vitrolin]

oh i see that now i had it confused with the thermal switch, which isn't shown in the schematic, but is in series with fuse and thermistor.

[Enzo]

Thermal switch?  Do you mean the thermal fuse inside the transformer?  That is usually not in a schematic because it is not a separate part, it is part of the transformer.

[phatt]

And don't forget TSA1 (Thermal cutout) mounted on the heat sink as well.
I worked on one of these amplifiers a while back,,, watch out for heat issues on R172/173 and R160/161.
Those were running so hot they had burned the PCB and de-laminated the traces. (not much R/D from Fender design team went into this one )
CR56/57 were also overheating. Expect finger burns from them.
If I recall correctly, I had to remount those parts off board.
R37,38,39 (although not as hot) were raised higher off the PCB to keep the heat off the PCB.

Phil.

[Vitrolin]

Thermal switch?  Do you mean the thermal fuse inside the transformer?  That is usually not in a schematic because it is not a separate part, it is part of the transformer.

i was referring to TSA1....was aware that the transformer had a thermal fuse inside i is shown on the 2nd page, but i had i confused with one of the primary windings, i feel a bit stupid now.

when i get it up and running i wonder what might burn.

And don't forget TSA1 (Thermal cutout) mounted on the heat sink as well.
I worked on one of these amplifiers a while back,,, watch out for heat issues on R172/173 and R160/161.
Those were running so hot they had burned the PCB and de-laminated the traces. (not much R/D from Fender design team went into this one )
CR56/57 were also overheating. Expect finger burns from them.
If I recall correctly, I had to remount those parts off board.
R37,38,39 (although not as hot) were raised higher off the PCB to keep the heat off the PCB.

Phil.

when i first opened it i thought the heatsink to be somewhat underrated event though it is directly on chassis

[phatt]

This stuff is made to a price not a perceived brand name quality so they only add enough to just cover it,, any more and the thermal switch shuts it all down. (kinda clever but still smells cheap ) 

A chap asked me to look at a Fender BXR bass head (similar era and heat sink design)
The plastic sticker on the back panel had melted off and was now unreadable.

The Amp kept shutting down even with a fan on it. He admitted he played it loud to keep up with the bands high sound levels.
I added a big chunk of alloy and never heard another complaint.

BTW, the triode is only used as a diode so it really adds nothing to the sonic result. But if it has a valve it will sell more units.
Phil.

[Enzo]

There is no twiddle pot, but sometimes bias needs to be adjusted.  They are not designed cold enough that all parts variances will fall into favorable ranges.  If it is burning up with heat, it needs to be cooled bias-wise.

[J M Fahey]

All 60/8 and 100/4 SS amps use something very close to 30+30VAC, 120-150VA (2 to 2.5A) so *many*  will do, even dead amp :"pulls" (think Peavey Bandit, Marshall VS100, Crate 100/120 , etc.) which you might have for peanuts at some Tech's junk pile.
Only difference is that yours has an extra 6.3VAC 300mA tap for the tube, but in any case you can add a tiny cheap extra transformer for that.

[Enzo]

Juan, in this case, no extra transformer needed.  For the single tube heater, they derived a 12.4vDC supply tapping off the main +40v rail.  The two zeners that do that are right next to the tube on the drawing.

[Vitrolin]

i had a moment today so i powered it up, R113 started to smoke so i guess that the heatsink was slightly underrated, but ill chaeck up on it if i get som time this week

[Enzo]

R113 doesn't burn up because of the heat sinks, it burns because Q13 is conducting too hard, and is likely defective.  Especially if R115 is not also burning.

[Vitrolin]

R113 doesn't burn up because of the heat sinks, it burns because Q13 is conducting too hard, and is likely defective.  Especially if R115 is not also burning.

yes, my point was that the heat sink didnt do it for output transistors so at least on died, in this case Q13 shortet.