50w Build started, have a couple of questions

[Explorerman]

Cheers mate, I might order the Hammond - who knows when the Heyboers will become available again.

Once the Heyboers do become available again, would it it worth swapping out the hammond later on? Would there be any improvement or difference?

[danman]

I wouldn't worry about swapping the PT unless it doesn't deliver the voltages you were hoping for. OT's are a different story but even they are highly controversial. Everyone has their favorites and Hammonds are no slouch in the tone deptartment.

[Explorerman]

APD have Heyboer 50w PT’s back in stock! It’s on its way.

[danman]

Great news!

[Asphaltbouncer]

How is this coming along?

[Explorerman]

Apologies, this has been on a standstill till I received my PT (APD Heyboer) working away, etc. Anyway, I finally installed the PT last night. I haven’t put the board in yet, I’ll do that once the PT is up and running and voltages are where they should be.

I’ve connected the mains, the heater wires + CT, the HT + CT, (CT’s to their Larry ground points). I’ve only powered the HT up to the open standby switch. However, I’m only getting a reading of 297VDC to ground at the +ve side of the the rectifier (same as hot side of standby switch), does this sound right? I’ve used the 1000V rectifier from Valvestorm.

Also, I’m getting 6.33VAC at the heaters with tubes out, but with all tubes in, this drops to 6.1VAC. Does this sound right? The tubes have nothing else connected - heaters only. I’ve used 18G wire for heaters.

Mains: 236VAC
HT: 646VAC
Lamp: 115.6VAC
Heaters: 6.33VAC unloaded, 6.10VAC loaded
Rectifier +ve to -ve: 590VDC

I’ve connected the 240VAC wire of the PT primary not the 220VAC Tap.

Let me know your thoughts, thanks.

[danman]

Are you plugged into a light bulb limiter? If so, voltages will be slightly low with the limiter. The B+ voltage will also read low if the filter caps are not installed. Once the caps are in the circuit, the DC voltage will come up.

[Explorerman]

Ah no worries, I thought that might be the case. No, this is without the limiter, I had even lower voltages with the limiter in circuit.

So do you think 6.1v on the heaters is ok?

[danman]

6.1 is well within the 10% variance normally seen so I'd say your fine. It could be that your wall voltage is running a touch low the day that you took the readings. A couple of volts difference at the wall will make a significant change inside the amp. Your B+ voltages shouId rise above 400v once you get the filter caps hooked up. I think you are in good shape to proceed.

[Explorerman]

Thanks @danman sounds good. I was a little bit worried about the PT, long story short - I’m in Australia, my brother was in Canada recently, so to save on shipping I had the PT delivered to his extended family in Canada. When he got back to Australia, the package was all unwrapped and it was loose in his luggage - most likely by customs, he was worried it may have been damaged moving around in his luggage. There are no visual signs of any damage, hopefully it’s all good.

The mains voltage is normally stable around 236v in my area.

[danman]

The transformer should state the exact primary voltages that it was designed for. If your wall voltage is just a few volts lower than the design voltage, that would explain the slightly low filament reading. As long as it stays within 10% of expected voltages, your amp will do just fine.

[Explorerman]

Thanks for the advice! Next step is to drop the board in, before I do, can you see anything on the attached pic that I should change (mainly regarding lead dress)?

- I’ve left some extra length in the OT prim red lead in case it’s out of phase and I need to swap the red and white (I’ll shorten that once it’s all working).

- I’ve implemented the Larry grounding

- The heater wiring between PT and V5, I didn’t run this as per the instructions, the way I have it here it doesn’t run paralleled with any other wires and tried to keep close to the chassis and runs alongside the wiring between V5 and V4. Any issues with this? Or should I change it as per the instructions running diagonally direct to V5?

https://www.dropbox.com/s/1a78d57dy8360 ... .HEIC?dl=0

[danman]

Your picture isn't showing up. If you posted a pic in your thread at the Telecaster forum, I'll take a look and let you know if I see anything. I have been following your thread over on that forum also.

[Explorerman]

Sorry mate, just added a link above (it wouldn’t let me attach for some reason).

Yeah thought I’d check over there as well as I didn’t get any replies after a day (I can be impatient sometimes lol), a couple of the guys over there were really helpful when I did a 5E3 build a year or two ago.

[danman]

Everything looks good to me in your pics.

The fellas over at the Tele Forum are a great bunch but they tend to focus on Fender amps mostly. I read your post earlier where you mention "Larry Grounding" when asked about a ground scheme. Be prepared for some kickback on that as most of those fellas completely disagree with the Larry grounding method. Over the years the group has begun to favor the "split ground" method or the "single bus" method with only one point of contact to the chassis (not including the safety ground for the power cord). Having so many points of contact with the chassis like the Larry method uses just seems wrong to them...lol. I have built several amps with the Larry method and they all turned out quiet. In the past few years I have moved on to the single bus method as it is very easy to implement and always produces a quiet amp.