68 Custom Princeton Reverb - 240v mod?

Blackdream

I don’t know if the Princeton is the same as my Deluxe, but this is what I did.
Disconnect the reverb jacks and speaker jack.
Disconnect clip holding mains wire.
Remove top back panel, power valves and rectifier valve.
Remove 3 screws holding chassis to the rear underside of the top
Remove the 4 screws at the top
Slide chassis out

Keefy

ICBM said:

Lewy said:

Interesting - would that include something like the Custom 57 Champ do you suppose?

EDIT: actually don't worry - just looked inside mine and the black-with-white-stripe wire isn't connected to anything so presumable these already come wired for 240v

No - I checked the schematic and on that model, 240V is white/black and 230V is white - neutral is black.

Unless you bought it second hand, it will be 230V - under EU law, Fender *must* supply the amps set for that, which is the official voltage.

(I doubt that will change now, even though it would have been one of the possible slight benefits...)

Luckily, Australia and New Zealand still officially use 240V, so the tap is fitted to most (but not all - the Pro Junior is an exception) Fender amps.

I'd better check my PR68 at some point, not sure how old it is - mains around here is typically 249V!

fandango

UnclePsychosis said:

Has anyone got a "howto" for getting inside a PRRI? 

Is it literally just as simple as undoing the four screws on the top and sliding the chassis out? Are there any nuts or bolts to watch out for? 

First, make a note of the reverb tank connections on back of the amp.
Next, the four screws on the top back panel.
Then the four screws on top.....

soma1975

ICBM said:

soma1975 said:

Would this be the same on the 68 Custom Deluxe reverb?

Yes - in this case it’s P2 and P8. The 230V wire is the white/black stripe, and the 240V the plain black, on almost all the models as far as I know.

Edit - not all. The '57 Champ appears to be different.

Just had a look and not sure if I am looking at the wrong thing but P8 appears to have a purple cable in it on my amp.

ICBM

The purple and white/black wires have been incorrectly fitted the wrong way round. That's a bit naughty - it *shouldn't* make any real difference since it will just reverse the connections to the PT primary (effectively swapping live and neutral, which is what those two pins are connected to), but I would question why someone at the factory didn't follow the standard procedure shown on the layout and schematic.

You can still swap white/black (CP1) with black (CP8) to get 240V operation though, if you don't want to swap the violet and white/black first.

soma1975

Brilliant thanks matey. 

fandango

Blackdream said:

I don’t know if the Princeton is the same as my Deluxe, but this is what I did.
Disconnect the reverb jacks and speaker jack.
Disconnect clip holding mains wire.
Remove top back panel, power valves and rectifier valve.
Remove 3 screws holding chassis to the rear underside of the top
Remove the 4 screws at the top
Slide chassis out

I didn't find it worth the hassle of removing the valves from my 68 CPR.

Tested it and works fine.


Also ... here's a question for the experts. When running the amp at 240v (instead of 230v) will there be a little more heat generation?

ICBM

fandango said:

Also ... here's a question for the experts. When running the amp at 240v (instead of 230v) will there be a little more heat generation?

No, less. That's the whole point - and in some amps (especially the Blues/Hotrod Deville) to reduce the valve voltages, which can cause failures because these amps operate them right at the upper limit of their ratings.

Basically the problem is that the amp is set for 230V but is actually receiving 240V, so all the internal voltages are increased by 4.3% above their designed values. That doesn't sound much, but it's more complicated because power is proportional to the *square* of voltage, so the dissipation in the components goes up by 8.9%, which is starting to get noticeable. It won't make the amp fail immediately or even soon, but over time it does stress some parts more than they need to be.

fandango

ICBM said:

fandango said:

Also ... here's a question for the experts. When running the amp at 240v (instead of 230v) will there be a little more heat generation?

No, less. That's the whole point - and in some amps (especially the Blues/Hotrod Deville) to reduce the valve voltages, which can cause failures because these amps operate them right at the upper limit of their ratings.

Basically the problem is that the amp is set for 230V but is actually receiving 240V, so all the internal voltages are increased by 4.3% above their designed values. That doesn't sound much, but it's more complicated because power is proportional to the *square* of voltage, so the dissipation in the components goes up by 8.9%, which is starting to get noticeable. It won't make the amp fail immediately or even soon, but over time it does stress some parts more than they need to be.

Thank you ICBM. Much appreciated.

noisepolluter

I think I’m going to wait till I can get the local tech to do this for me - I can’t get the connectors off without clipping the cable tie on the wire bundle, and I’m not confident I could tie it back together as neatly. 

IsambardKentucky

Would this be an issue for most amps imported to the UK from outside the EU?

ICBM

IsambardKentucky said:

Would this be an issue for most amps imported to the UK from outside the EU?

It depends whether they’re designed with multiple voltage settings or just a universal “220-240V” one. Even some Fender amps (eg the Pro Junior) have that. Some others have either 220V or 240V but no 230.

Any amp that has a 230V setting must be safe to operate anywhere in the EU, including the UK (as it was!) - it’s just that if it also has a 240V setting it’s better to use it in the long term.

fandango

The 230v is all to do with EU harmonisation, and with a +10% to -6% tolerance it covers both 220v in mainline Europe and 240v in the UK, without having to make one group change to the other group’s standards.

ICBM

fandango said:

The 230v is all to do with EU harmonisation, and with a +10% to -6% tolerance it covers both 220v in mainline Europe and 240v in the UK, without having to make one group change to the other group’s standards.

Exactly - but like many 'common standard' things it's actually a fudge and all it's actually done is introduce *another* standard.

The problem is that the voltage is fixed by the transformer ratios in the substations, so unless/until they're all replaced then nothing has actually changed. I assume that any new ones are made to a true 230V, so over time the problem will eventually be resolved - but I could be wrong about that. Even if I'm not, it will be a very long time - substation transformers don't often fail.

UnclePsychosis

Did my 65 PRRI this evening.

For a job thats trivially easy it really was rather nerve-wracking, but maybe its because I'm a big wuss. Those bloody spade connections are a nightmare to get off. I know they need to be secure but I wasn't half sweating by the end :-D

Need to have a proper play tomorrow (kids are in bed now) to see if it has made any tonal difference (not expecting much). Weirdly I think the trem ticking is slightly louder but that may be imaginary. 

crunchman

Is the amp likely to need rebiasing afterwards?

noisepolluter

UnclePsychosis said:

Did my 65 PRRI this evening.

For a job thats trivially easy it really was rather nerve-wracking, but maybe its because I'm a big wuss. Those bloody spade connections are a nightmare to get off. I know they need to be secure but I wasn't half sweating by the end :-D

Need to have a proper play tomorrow (kids are in bed now) to see if it has made any tonal difference (not expecting much). Weirdly I think the trem ticking is slightly louder but that may be imaginary. 

Did you have to clip the cable tie on the big bundle of leads?

When I did my DRRI it actually made the trem tick quieter - though that’s a different circuit. 

My PRRI trem is only audible by the way it chops off the reverb - which I quite like actually 

UnclePsychosis

No there was enough slack that I didn't need to adjust the cable ties at all.

As for the tick, the amp is pretty quiet anyway. It only gets really ticky with the reverb cranked higher than I'd ever use it. I'll need to have a proper listen tomorrow though, tonight I just turned it on and stuck my ear next to it to listen to the noise so was probably hyper sensitive. 

fandango

Okay, having done the 230-240 mod a few days ago, today was the first day I had a proper (relative speaking) go at giving my 68 CPR something to think about.

Playing a Les Paul through the amp, and there's reduced hissing and noise. With/without reverb. Ditto tremolo. And ditto both. And then I put a few pedals in the way, and it's quieter. Nothing scientific, but an aural improvement. Caveat. My impression of the sound/tone "before mod" could have been tainted by lack of use over the previous 2/3 months.

The biggest thing (again relative) is that there appears a more distinct difference between the two inputs. I can hear the low end on Input 2 as distinct from the brighter but possibly fuller Input 1.

Wow.

Channelling the words of Arsene Wenger whenever a player returned to action after a long absence... it's "like a new amp". 


PS - It's got a Celestion Neo Creamback in lieu of the stock Ten-30.

UnclePsychosis

Has definitely made my PRRI quieter. Not sureI could claim any other difference but I'm happy with that tbh.