ODS #183 Build

[martin manning]

I like to use these 3/8" square Bourns trimmers, 3386F. They are 1/2W Cermet, and PCB mount, but you can bend the leads straight out and solder them to the trumpet bell part of the eyelets. https://ampgarage.com/forum/viewtopic.p ... 77#p428877

[galtjunk]

Heyboer makes a twin pt with dual 6.3v taps so you can power your relays.
They have enough ma to power a quad of El-34's and the pre amp tubes plus some.
They also make a suitable OT.
Call Phil at Heyboer. He will find the transformer numbers for you.

The label on my PT reads
Blackface Twin
HTS-10359
9961816

[pfarrell]

Here's some other transformers for the record (Take a while to get) since we seem to have a little running list of iron options in this thread:
PT/ Edcor XPWR127 (This has a 12V tap! and was recently "re-added" to their site)
OT/ Edcor CXPP100-2.2K

[pfarrell]

I was also wondering if there's a high resolution image of the layout file here:
https://ampgarage.com/forum/viewtopic.php?f=5&t=13095
It's hard to see where some of the connections are made under main board (red/brown color contrast issue)... Have schematic of course, but just figured I'd ask.

[ijedouglas]

You can use the layout from the #0124 file https://ampgarage.com/forum/viewtopic.php?f=5&t=5719. The under board wires are the same

[pfarrell]

PSU parts showed up today—so now I can verify the layouts of the eyelet boards for the other parts of the amp. And a super kinda member up here sent me an amazing cache of NOS parts!!! Just WOW.

Was working on front and rear panel layouts... Generally there seems to be some variance in the rear layout not sure what's original vs. mods. etc...
I'm going to use an IEC, I've been swayed by the valve wizard and will likely delete the standby switch (let opinions fly if they must)... the drilling layout file doesn't include the wattage switch, but does include the impedance dial, which isn't on the #183 layout file... I have a picture of the front and back of #182, different again.....
Just wondering what the definitive idealized layout is, even if modded... Also the 2 schematics I have one specs 3 amp and the other 5 amp for mains fuse (inrush on a larger non-original trafo?)... I was under the impression that 3 would be adequate...Merren iron? hmmm....

On the front for the OD section I see different nomenclature for the pots. "Level", "Ratio" vs. "Drive", "Volume"....

[martin manning]

The pinned 183 post in the files section is probably the most accurate wrt the original. Personal preference on the impedance selector and half-power switch. Drive/Volume on 183 has the same functionality as Level/Ratio on other amps. No standby? SMH.

[ijedouglas]

I would highly recommend a standby switch. SS rectifier does not have the soft start of a tube rectifier...

I would ditch the 50/100 switch. I don't think you will use it but if you ever need to, pull 2 tubes and you are good to go.

5A for the 183

[pfarrell]

Thanks guys. I try to listen—I'll put in a standby switch—no head shaking required .
What's the story with the test points? Never had such a luxury on any of the amps I've built. I see 5 drill holes on the "chassis holes guide", looks like 4 points noted on the #183 layout file, grids/5K6.

[ijedouglas]

I've never used the test points but they are there for the 1 Ohm bias sensing resistor so you could set the bias without pulling the chassis. Personal preference, I prefer building it as close to the way HAD built it

[Chris Brown]

Thanks guys. I try to listen—I'll put in a standby switch—no head shaking required .
What's the story with the test points? Never had such a luxury on any of the amps I've built. I see 5 drill holes on the "chassis holes guide", looks like 4 points noted on the #183 layout file, grids/5K6.

These are usually wired to the cathodes along with a 1ohm resistor to ground from the cathodes. It gives you an easy way to set the bias with reasonable accuracy. The 5th hole is usually for a ground test point so you can stick one end of your meter in the ground test point and the other in one of the cathode test points.

[martin manning]

I've never used the test points but they are there for the 1 Ohm bias sensing resistor so you could set the bias without pulling the chassis. Personal preference, I prefer building it as close to the way HAD built it :)

HAD probably didn't want to make it too easy for anyone else to mess with it ;^)

[pfarrell]

...Bit of meditation on this tonight (nothing locked in yet)....Do you guys tend to solder in all the leads extra long? (I'm used to working with turrets and not much is buried under the board...)

PF-183_02.jpg

[ijedouglas]

Do you guys tend to solder in all the leads extra long?

I try and measure inside the chassis and then give myself a little extra. I solder up the whole board with all wires before final installation into the chassis.

[pfarrell]

Some part swaps based on member observations, stuff I missed (which amp uses that extra eyelet there? In the PI tail zone?)... made the under board connections and the one ground leg... nothing soldered yet, i'll put the orange drops in some silicone glue...I have the PSU parts in hand and can marry them with Martin's layouts to make sure it all fits lead spacing wise and then make the PSU board, etc. Taking it slow so I end up with a working amp! Still sorting out iron. I do have chassis face plates though. Maybe I can start cutting holes if I can get the iron measurements confirmed and also the head cab....I can cut some wood for the 1x12 speaker box while I wait on Iron....

PF-183_03.jpg