ODS #183 Build

[pfarrell]

Bit more progress....

PF-183_11.jpg

[Abe5150]

What iron did you go with???

[pfarrell]

What iron did you go with???

Trying to nab a full compliment from Merren Audio, 100W Marshall set. Awaiting shipment....should be any time now...
I do also have a PT and OT from Edcor in hand...even though they say their shipping is months out—my experience has been that you will get stuff from them usually inside a month, often faster. I'll likely make the PCB version of #102 or #124 because why not and then I can do some quasi-comparisons. Maybe a second #183...So, Edcor iron in that one....Obviously, perhaps, considerably more satisfying to build completely from scratch...? It's all fun.

[Abe5150]

Nice! Merren X formers sound interesting a lot of builders use those in high end Marshall builds.

[pfarrell]

Long time coming! Now I need to see if I have some 2.5" bolts ....and see if I can get Chris to give me some wiring diagrams. Whew.

PF-183-OMG-Iron_12.jpg

[ijedouglas]

Whew!

Here are the wiring diagrams:

T2562
PRIMARY:
ORANGE= Neutral Common
WHITE/red stripe = 100V Japan
RED= 120V
BROWN= 220V
BLUE= 230V
PURPLE= 240V

SECONDARY:
THICK BLACK wires= 6.3V Heaters
THICK GREEN WIRE= Center-Tap for Heaters goes to ground...
BLACK and BLUE wires= High Voltage goes to diodes or stand-by .... 465V
BLACK/yellow and BLUE/yellow = High Voltage goes to diodes or stand-by ....500V
YELLOW= High Voltage Center-Tap ...goes between the first set of filter caps..
WHITE= bias
GREEN = ground for bias winding

C1998
PRIMARY:
RED = V4 & V5 plate, Pin#3
WHITE = Center-Tap... B+
BROWN = V6 & V7 plate, Pin#3

SECONDARY:
BROWN = Ground chassis
BLACK = 4 Ohms
YELLOW = 8 Ohms
GREEN = 16 Ohms

[pfarrell]

Thanks a million Ian—have you built one of these amps before?

[martin manning]

I have to say it's a bit disappointing that you received those with no diagrams or mounting bolts. I would take Ian's input, put 12VAC on the PT's orange and red (assumed 120V Primary), then check all the other windings for 1/10 of the expected voltages. Likewise on the OT, put 10VAC on the primary and check the secondary leads for voltage ratios corresponding to 4, 8, and 16 ohms.

[pfarrell]

Thanks Martin—Ian has also reminded me that I need to update my (your) bias board for the "Marshall" connections...Also, I agree about the mounting bolts etc... I think Chris has a lot going on at the moment—I'm happy to have the iron in hand finally—I think I'll also add bolts to the OT instead of the center point bolts... bit of flex there..

[ijedouglas]

For others interested, this is how I wired the PT:

T2562
PRIMARY:
ORANGE= Neutral Common - USED
WHITE/red stripe = 100V Japan - TAPED OFF
RED= 120V - USED
BROWN= 220V - TAPED OFF
BLUE= 230V - TAPED OFF
PURPLE= 240V - TAPED OFF

SECONDARY:
THICK BLACK wires= 6.3V Heaters - USED
THICK GREEN WIRE= Center-Tap for Heaters goes to ground... - TAPED OFF. Used 100R balance resistors
BLACK and BLUE wires= High Voltage goes to diodes or stand-by .... 465V - USED
BLACK/yellow and BLUE/yellow = High Voltage goes to diodes or stand-by ....500V- TAPED OFF
YELLOW= High Voltage Center-Tap ...goes between the first set of filter caps..- TAPED OFF
WHITE= bias - USED
GREEN = ground for bias winding - USED

[martin manning]

... Oops

[martin manning]

Thanks Martin—Ian has also reminded me that I need to update my (your) bias board for the "Marshall" connections...Also, I agree about the mounting bolts etc... I think Chris has a lot going on at the moment—I'm happy to have the iron in hand finally—I think I'll also add bolts to the OT instead of the center point bolts... bit of flex there..

To be clear, per Ian's description (465V HV secondary on the PT) the HV rectifier board should be configured for the Fender (two phase) rectifier, not the Marshall FWB arrangement. Good idea to add the corner bolts to the OT. That will reduce mechanical vibrations and help to keep it quiet.

[pfarrell]

Okay—that's confused me now... Ian sent me a drawing of his bias connections and it's analogous to your Marshall config...?
It's beyond my current level of understanding to divine the differences for myself... Assuming it's something to do with how the transformers are wound? The Merren set is clearly advertised as a Marshall replacement...

[martin manning]

Sorry, The 465V labeling confused me... That has to be peak (and DC) voltage, as there is no CT. I would rather see that marked 330 VAC, indicating RMS voltage. In any case, yes, Marshall FWB configuration.

[pfarrell]

Cool... So this (just redid it and added the extra eyelet).... 13K there on the dropping resistor. 100V bias tap.

PF-183_13.jpg