NOS John Mayer Sig / Wonderland 100W

[rccolgan]

Re: higher voltage on v1 (and in general) What is your power transformer's HT windings? 320-0-320 or 345-0-345? Curious if this might be a point of interest.

[dbharris]

Re: higher voltage on v1 (and in general) What is your power transformer's HT windings? 320-0-320 or 345-0-345? Curious if this might be a point of interest.

It's 320-0-320, Classic Tone 40-18004. Since Two-Rock ordered special "low wind" PTs I expected voltages to be a bit high, but I thought the power tubes would run hot too but it is just the 9 pin tubes. I did a little tube rolling but I was getting voltage swings of about 5v usually and the TAD novals tended to run at lower voltage than most of my other tubes. I usually wait until the amp is burned in to really roll tubes.

Originally I was thinking I might add a 16uf 500v filter before the first node and drop some voltage with a zener after it to lower B+. But since the power tubes are pretty close to Taylor's voltages, I think it will be easier to increase the first dropping resistor.

Did you measure voltages when you were inside those other amps or just look around?

-Dan

[rccolgan]

The real Two Rock I was poking around with measured 656vAC loaded HT measured at the rectifier input, 430vDC B+, 402vDC B3, 257vDC B4, 250vDC B5. 164vDC measured on V1A. I admit I did not check the wall voltage or bias current while taking these measurements. It was a little rushed and I was sweating bullets while poking around.

Curious what the 320-0-320 measures loaded in AC with your PT. I have not experimented yet with that PT but planning on it soon

[dbharris]

The real Two Rock I was poking around with measured 656vAC loaded HT measured at the rectifier input, 430vDC B+, 402vDC B3, 257vDC B4, 250vDC B5. 164vDC measured on V1A. I admit I did not check the wall voltage or bias current while taking these measurements. It was a little rushed and I was sweating bullets while poking around.

Curious what the 320-0-320 measures loaded in AC with your PT. I have not experimented yet with that PT but planning on it soon

Yeah I bet! Very nice of the owner to let you have a look inside.

Those voltages you measured are right in line with Taylor's layout except the B+/plates in the amp you spent time with were about 15 volts lower and everything else is within range of what you would expect with fluctuations to mains voltage.

I did not measure the loaded AC. But I will the next time I pull the chassis. May be 2-3 weeks. I need to pull together another Mouser order with D'Lator parts too.

I have burned the amp in for about 15 hours and then played it again today for 40 minutes. It is a bit smoother sounding now. Will burn it in another 10 hours or so on the dummy load.

I cooled down the bias a bit and my power tubes seem to be drifting apart a little too. One pair is at 32ma and the other at 36.4ma right now. When I ordered the Tubes from AES they accidentally sent me a matched pair, not quad. So, they sent another matched pair a few weeks later with similar measurements...maybe they were not very tight to begin with.

-Dan

[dbharris]

I did order some ... I think one is actually metal oxide that Mouser has mis-categorized? Can't remember the brand off hand, maybe Yageo?

I received metal oxide for both Yageo and KoaSpeer from Mouser recently and notified them. Details in this thread

These were the resistors that I was referencing. Not the best quality picture, but the red Vishay PR01 and pink Yageo FMP have the appearance/feel of metal oxide. Sort of rough and dull. The blue Vishay above is the newer MBE/SMA 0414 Series 1 Watt and about the physical size I would expect. I also put a Vishay RN60D next to it for comparison purposes.

Here are the data sheets:

Yageo https://www.mouser.com/datasheet/2/447/ ... 714047.pdf

Vishay https://www.mouser.com/datasheet/2/427/ ... 762580.pdf

They are both described as metal film on ceramic body. I'm no EE so not sure if this is different from a "traditional" metal film resistor.

-Dan

[neskor]

yesterday I had a chance to play John Mayer Signature and managed to take some nice hi-res pictures
I will post this one, if you want more please let me know

[norburybrook]

yes please,

shame the pre amp is covered with a layer of board.


What's with those 4 voltage regulators on the main power/filter board?


M

[neskor]

I tried to take some pictures under the board

[neskor]

I'm not sure about those diodes

[rootz]

Diodes: https://ixapps.ixys.com/DataSheet/DSEI12-12A.pdf

[jfs322]

yesterday I had a chance to play John Mayer Signature and managed to take some nice hi-res pictures
I will post this one, if you want more please let me know

That's not a John Mayer Signature. That's a Two-Rock Custom Reverb Signature, Version 2, 50-watt.

[rootz]

Scratch that, this is not a Wonderland/JM signature!

[rootz]

I think this is a CRS mk1, the one with the Fender type reverb. Biggest hint: paralleled triodes V3 as reverb driver.

[jfs322]

I think this is a CRS mk1, the one with the Fender type reverb. Biggest hint: paralleled triodes V3 as reverb driver.

It is a version 2. The blue anodized chassis was not a feature on the version 1; it was introduced on (and was special to) Version 2. You can also tell by the date: 2007 was after version 1 was retired and version 2 was introduced.

[neskor]

I think you are right, this is probably V2
There is also a signature on the back, so I assume this is JM signature. My wrong