Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: Vitrolin on February 18, 2016, 06:34:33 PM

Title: Performer/Roc-pro transformer
Post by: Vitrolin on February 18, 2016, 06:34:33 PM
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
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 19, 2016, 01:15:35 AM
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.
Title: Re: Performer/Roc-pro transformer
Post by: Vitrolin on February 19, 2016, 09:07:18 AM
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...
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 19, 2016, 06:33:43 PM
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
Title: Re: Performer/Roc-pro transformer
Post by: Vitrolin on February 20, 2016, 01:48:29 PM
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.


Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 20, 2016, 06:14:35 PM
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.
Title: Re: Performer/Roc-pro transformer
Post by: phatt on February 21, 2016, 05:49:50 AM
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 :loco)
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.
Title: Re: Performer/Roc-pro transformer
Post by: Vitrolin on February 21, 2016, 06:32:27 PM
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 :loco)
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
Title: Re: Performer/Roc-pro transformer
Post by: phatt on February 21, 2016, 07:18:48 PM
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. :o

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. :tu:

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.
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 21, 2016, 07:58:22 PM
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.
Title: Re: Performer/Roc-pro transformer
Post by: J M Fahey on February 22, 2016, 08:25:58 AM
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.
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 22, 2016, 06:16:58 PM
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 :trouble drawing.
Title: Re: Performer/Roc-pro transformer
Post by: Vitrolin on February 22, 2016, 06:54:52 PM
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
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 23, 2016, 11:25:58 AM
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.
Title: Re: Performer/Roc-pro transformer
Post by: Vitrolin on February 23, 2016, 06:44:10 PM
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.

Title: Re: Performer/Roc-pro transformer
Post by: J M Fahey on February 23, 2016, 08:56:03 PM
Why do you think so?

Thousands of RocPro/Performer amps happily out there with the exact same heat sink assemblies (typically somne thick aluminum spreading heat on the whole aluminum panel) .

You have dead transistors, no doubt, but something else killed them.

A common mistake is to unbolt transistors from the heat sink assembly and turn amp on "just for a minute" , "just to check that everything is fine".

That test is usually one minute too long to kill outputs.

Annoying as it seems, board must be pulled to replace suspects, but then must be fully greased and mounted to test.

If you need to repeat everything because some problem remains, so be it :(
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 24, 2016, 07:29:21 AM
What Juan said^^^^

You are assuming the output failed because of the heat sink without any evidence to support that.   Thousands and thousands of those amps are out there and not blowing up.  They use the same chassis/sink design on a number of other models too.  Lots of things cause transistor failure.  Heat can certainly be one of them, but not the only one.
Title: Re: Performer/Roc-pro transformer
Post by: g1 on February 24, 2016, 12:11:27 PM
  Some of those Fenders use the heatsink "bar" that mounts to the chassis.  From what I recall, it can be mounted upside down and if so, doesn't mate correctly to the chassis.  Or there can be dried up heatsink compound that interferes with proper heat transfer.
Title: Re: Performer/Roc-pro transformer
Post by: Enzo on February 25, 2016, 03:03:58 AM
You may be right.  I have reassembled them wrong then been ticked off that I had to take it apart because it didn't fit.  But I don't recall being able to leave it in wrong, some part of it was in the way.  The main headache was I was going to have to get MORE grease on my fingers to turn it over.
Title: Re: Performer/Roc-pro transformer
Post by: DrGonz78 on February 25, 2016, 03:47:34 AM
Yeah I got in a habit of drawing an arrow with a black sharpie on the side of the heat sink bar to make it easier to put it back together correctly the first time. I have an old Roc Pro 700 sitting in the shop and mine gets pretty hot. I have been meaning to pull it out and check the bias etc. The amp is in such crap condition that I forgot about it for a while now. I will have to give a good look over soon.