Princeton Reverb clone with 12" speaker?

[tubeswell]

Does anybody here belong to the Weber Amps N More forum? I have applied for login registration to discuss this with a few builders of this kit over there, but they are a bit slow responding to my registration request, and if anyone here can put in a plug for me over there to get things moving along that would be much appreciated thanks.

Cheers

[hasserl]

Does anybody here belong to the Weber Amps N More forum? I have applied for login registration to discuss this with a few builders of this kit over there, but they are a bit slow responding to my registration request, and if anyone here can put in a plug for me over there to get things moving along that would be much appreciated thanks.

Cheers

OK, I put in a plug for you. I haven't been around there much lately, and I had to reset my password to get in! But got that done then posted a plug for you in the Bull Pen forum. Hope someone see's it and moves on things for you.

[tubeswell]

Thanks hasserl.

[tubeswell]

I have been getting feedback from one or two Ozzie customers of Weber VST that their EU version of the PT for these amps (W025130 EU) is a bit of a fizzer. Apparently several of them have burnt out with overheating after a relatively short period of time.

The HT winding is rated for 150mA, which should theoretically be fine for 6V6s (and the US -120V equivalent apparently doesn't have the same problem), and the 6.3V winding is rated for 5A and the 5V winding is rated for 3A. So I'm wondering if it could be something to do with the overall power handling capability of the 240V version. (Not that this should matter should it? If the primary voltage is twice as high, then the current draw will be half as much on the primary - all other things being equal - I would've thought. E x I = P)

If anyone has any experience with the Weber EU PTs here, I'd be interested to hear what you have to say.

[JoeM]

I've read posts refering to bad EU version PTs, I'm not sure if Ted ever resolved that issue. Hopefully you didn't get one with problems.

[tubeswell]

Hmmm... Do you think the Weber's would mind/object/take a law suite against me, if I got the PT in question reverse engineered by my tried and true blue local winder to assess any potential reliability issues and provide me with a full report and recommendations? He's a very experienced winder who has been in business for about 40 years and knows pretty much everything there is to know about winding PTs for "EU" voltages.

(I am seriously considering getting him to wind me an alternative one anyway).

[Steve Conner]

Just don't tell them you're going to do it, do it, and keep quiet about the results. If you find any flaws in the transformer, you then have a bargaining stick that you can beat Weber with.

Oops, too late, you already told us you're going to do it.

Maybe he wound for 220V. In the UK and presumably Aus too, it's 240+. My old workplace used to measure 250 once everyone had gone home. In Eastern Europe it can get down to 200.

[tubeswell]

Hi Steve

The Primary does have 220 and 240 taps. Maybe those guys whose trannies fried were wiring them using the 220V tap as you say. But how much more strain on the tubes would this have caused? (If indeed it was they which had gone and taken out the PT with them. How likely is that??. It would've only made the secondaries 8% higher by my (- probably faulty) reckoning.)

[tubeswell]

Well I talked to my regular (NZ) Transformer supplier/winder earlier today and he mentioned that it was apparently quite a common problem for US suppliers of PTs to countries with EU voltages, where they don't understand the implications of 50Hz mains supplies when they wind PTs for "EU' voltages.

So then I quickly googled and found these, which have helped shed a little more light on the issue for me.
50 Hz vs. 60 Hz Power Transformers

Transformers
So a 230VAC 50Hz mains supply means you need about 20% more iron than a US 'equivalent'? (because of the bigger area under the sine wave function for the 230V 50Hz)

I am beginning to understand why the Weber EU PTs might not be up to the job, but I don't know if they have corrected the problem with what they supplied me or not (because this is the 1st time I've bought a Weber PT and I've got nothing else to compare it with). I have decided to get a NZ made replacement PT for it anyway. 2CW

[tubeswell]

FWIW, I've ordered a replacement Pt from the bloke who usually winds my trannys and it should be here within a week. When it gets here, I'll post a side-by-side pic for comparison with the Weber one that came with the kit.

[tubeswell]

Chassis Finished

Just finished the chassis today (the kit I got in Nov). Got a bit of checking to do before I test fire it. (I haven't heard back from CJ Sutton yet about whether the PT can handle 50Hz (240V), but I've decided to plow on with the standard kit PT anyway. I've got a back-up PT I can use it it fails). I've wired it for the 340-0-340 tap and with the 5V winding hooked up because I'm going to run a 5U4G. I put a couple of 1N4007 in series with the rectifier anodes on the high voltage winding as extra protection.

Incidentally I have rigged up a DC heater elevation on a little tag board with a 10 percent (195k/23K) voltage divider and a 47uF filter cap, which I'm running off the 'unused' filter cap node. The overall 218k doubles as a bleeder circuit.

As a workaround to the small holes in the el-cheapo lamp holder that came with the kit, I ran the heater winding to a 2 terminal tag strip and took the main heater wiring off that to the tubes on one side, and to the lamp on the other side. (Time will tell whether the lamp holder holds out - I couldn't get a standard Fender bayonet lamp holder to fit, - the rake angle on the front of the chassis was to sharp and there was no room in there)

Otherwise I pretty much followed the standard layout. (I guess I'll see whether how well the standard grounding holds up). I haven't wired up the footswitch yet, so I've got a few small miles to go with it before its ready to take out.

Otherwise, I can't really take much credit for the pretty appearance (apart from the assembly etc) because its a kit after all. I guess these blackface clones look better if they have the proper make-up (face plates and nice cab etc), but it just don't feel the same as when I get to hand make all the bits myself. Ah well I did it for the helluvit experience.

A couple of impressions for anyone who may be considering one of these kits. The kits looks real pretty, and apart from one or two bits which aren't difficult to find better quality substitute parts for, its seems like pretty good value for money.

The niggles are that I found the chassis front rake/angle off-putting when I found out I couldn't fit the standard fender lampholder, and I am a bit concerned about the stock PT's (that shipped standard with the kit) ability to handle 50Hz - might pay to order an after-market PT if you are in one of those 50Hz countries. I also had to get some other RCA jacks as the ones that shipped with the kit were sufficient to clamp the back faceplate on. 2CW

[JoeM]

Looks great! Are you pretty close to firing it up?

[tubeswell]

Yeah I fired it up yesterday - I've just got a helluva nasty hum issue to chase, which I'm working quietly away on. (Hum starts when the stdby is flicked on even with everything - vol, tone, levels etc all cut to zero - I haven't tried a different rectifier tube yet, the one I have in there now is a NOS Toshiba 5U4GB - but I've got a couple of spares so we'll see. Otherwise it could be bad grounding or poor lead dress near the cap/power switches etc. I have wired it initially so that the grounding is pretty much 'stock' BFPR, except I couldn't solder the filter cap can -ve lugs to the chassis, so they are all tied together and grounded at the main power amp ground return terminal strip - I might change that - the other thing I was thinking of adding was a separate pre-amp filter cap so I could ground that separately with the rest of the pre-amp at the brass grounding plate. I have the RT secondary grounded at the reverb input RCA jack, and the 220k grid leak for the recovery stage grounded at the Reverb Pedal/ Reverb Output RCA jacks. The main board grounds all go the the brass grounding plate. The pots ground to their respective back covers).

Also the biasing is hot, ~30mA even with the bias pot dialed to max negative bias, so I'll have to up the bias pot series resistor a bit.

[tubeswell]

Well I just heard from CJ at Weber VST, and he confirmed that they have added more iron (laminations) to the EU PTs a while back, and the one I've got with this kit is apparently one of those, so that's all good. Even so, he was very obliging and said to let him know if there were any issues as time went by.

[tubeswell]

I re-did the grounds today to get rid of some hum (and it worked to a certain extent). I now have a split ground with a separate pre-amp filter cap grounded with eth rest of teh pre-amp grounds at the bras grounding plate

Curiously the amp hums slightly with everything cut right back, but as I turn the vol up to 1 or 2 to hum completely disappears. Then as I turn the vol up to 4 or so, it starts to come back, so I turn up the treble slightly and the bass up slightly and the hum goes away again, but comes back if I keep increasing the vol, treb or bass. So what gives? (EMI coupling in the signal path?)

Amps seems to function normally in most other respects (trem needs taming a bit - but I'll work on that next)