Hot Rod Deluxe type:Pr246

[nosaj]

I've got a Hot Rod Deluxe PR246 I'm thinking the PT isn't putting out enough voltage on the HT(red wires) Disconnected unloaded I read 341 Vac. On the 1996 schematic B+ first leg is 431Vdc
.Problem is low volume So I started at the PT and here I am.
As usual I feel I'm missing something.
So how many schematics are there for the HRD?

I also have a R11 which looks like a Disc Cap by the black primary wire for the PT. It is missing the lower half of the coating on the Disc.

[glebert]

AC measurements are RMS, not peak, so when you full wave rectify it the DC voltage will be higher than the AC RMS. 341VAC sounds OK to me.

[The Dude]

To my recollection, I've never seen a transformer read low voltage. The transformer wouldn't be my first suspect. I'm not sure I'm looking at the right schematic (your link seems to be wrong), but I see RT1 input thermistor. Is that what you're reffering to? You give us transformer output VAC, but what is your B+? When the symptom on one of these is low output, I think preamp plate resistors first. That's what I most often see. Fender is kind enough to have test points on their schematics, so I'd scope through and see where your signal goes low.

[drewl]

Also if you have a bad filter cap it will drag the DC voltage down.

[Chuck H]

Ok... I actually read what you wrote. Disconnected PT voltages are already significantly lower than the published node voltage. So...

Is this the stock PT? And, does it offer alternative primary hookups?

[nosaj]

To my recollection, I've never seen a transformer read low voltage. The transformer wouldn't be my first suspect. I'm not sure I'm looking at the right schematic (your link seems to be wrong), but I see RT1 input thermistor. Is that what you're reffering to? You give us transformer output VAC, but what is your B+? When the symptom on one of these is low output, I think preamp plate resistors first. That's what I most often see. Fender is kind enough to have test points on their schematics, so I'd scope through and see where your signal goes low.

Yes RT1 is missing bottom half of coating like its cracked off.
Right now the board is out for resoldering cracked joints and replacing Filter caps.
The voltages were throwing me off as I tend to start at the plug going forward and making sure power supply voltages were right. Glebert said it was AC measurements are RMS, not peak, so when you full wave rectify it the DC voltage will be higher than the AC RMS. 341VAC sounds OK to me.

nosaj

[nosaj]

Ok... I actually read what you wrote. Disconnected PT voltages are already significantly lower than the published node voltage. So...

Is this the stock PT? And, does it offer alternative primary hookups?

Yes stock and and no alternate primaries just a white and black.

nosaj

[The Dude]

It's actually a bridge rectifier, so 340ish RMS ACV would be about right for the expected B+. There's nothing wrong with the PT.

[Chuck H]

I just did a sim on PSUD2 and it looks like other are correct. The raw AC of 341V should land around 440 rectified and loaded to 70mV plate and more for screens and preamp land around 445V. So that unloaded voltage actually looks right as noted.

[Enzo]

We have this backwards. Yes, the transformer is likely just fine, but what we really should do is see how the thing works and then explore the transformer only if the transformer seems to fall short. In other words if the schematic says B+ is 431v, then what is your B+? If it is roughly 430v, then obviously the transformer is working. We are concerning over the transformer with no reason to suspect it.

RT1 over by the power wires is a thermistor, and it may flake off, but if the amp powers up and works, it is likely OK. You could put in a new one, but flaking doesn't necessarily mean failure.

Look on your circuit board, it will have the year version printed on it. In my one file I see 1996 and 2001, and I think there are others.

[J M Fahey]

Problem is low volume

Fender is kind enough to have test points on their schematics, so I'd scope through and see where your signal goes low.

^^^^^^ THAT.
Feed J1 input 2 a 1 kHz sine at 4 mV and check AC voltages at: TP2 - 4 - 5 - 7 - 8 - 10 - etc.
Scoping is even better than plain AC voltage reading because it will show any weird wavforms.

Once you find something out of spec, post it here

Schematic states where pots are set to.

[vintagekiki]

... Problem is low volume ...

Run Output Test from schematics.
16.3 VRMS on 8 ohm load = 33W

The low power problem can be in tubes V3, V4 and V5.
Are the tubes new, or like new.

[nosaj]

We have this backwards. Yes, the transformer is likely just fine, but what we really should do is see how the thing works and then explore the transformer only if the transformer seems to fall short. In other words if the schematic says B+ is 431v, then what is your B+? If it is roughly 430v, then obviously the transformer is working. We are concerning over the transformer with no reason to suspect it.

RT1 over by the power wires is a thermistor, and it may flake off, but if the amp powers up and works, it is likely OK. You could put in a new one, but flaking doesn't necessarily mean failure.

Look on your circuit board, it will have the year version printed on it. In my one file I see 1996 and 2001, and I think there are others.

p/n 0059781000 Rev A 2002.

I'll answer voltage questions once I'm done reflowing and replacing the filters. Gotta get out to the country this weekend. In laws are back from Michigan.

nosaj

[g1]

If I recall correctly, some of those thermistors don't have the coating going all the way to the bottom. As your B+ is good, shouldn't be an issue anyway, just thought I'd mention it.

[nosaj]

Just a follow up. Recapped filters and bias cap. Reflowed main board and tube board put back together We got Volume plus( I now notice these models got to 12 never looked close ).
I'll check bias and output tomorrow had a 10hr day at the cabinet shop....we're now doing hurricane damaged houses now that peoples insurance money is coming in now.....


nosaj