Layout of the Ford Amp #102

[talbany]

Hi All
Attached is a Layout of ODS #102 the famous Robben Ford green light amp and what we know about it so far.. Most of the info was taken from this thread

https://tubeamparchive.com/viewtopic.ph ... sc&start=0

As well as notes from my own info on the amp..
here is some history of the amp as posted by Max in this thread
Amp 1:

RF got his first Dumble amp (#0102) in 1982. 4th generation "classic" ODS head, black tolex (or perhaps dark grey suede with vox grill) Later updated to skyline specs

the Pot # as well as the transformer # were taken from this amp..You can look up the # to find the pot tapers They were CTS..
At one time the amp did have the HV taper but was gooped so I don't know the values so this is a best guess as taken from the 094 schematic..If it was later removed I will specify in the layout
If anyone has any additional info such as coax type that would be awesome.. Look over the layout for errors and will be happy to revise update if needed..
Enjoy All and Hope this Helps!!
A BIG thanks to Brandon, Scott, Shad,Max, and others who gave this info so freely..

Tony

[UltraHookedOnPhonix]

Tony, you're totally kicking a$$ and taking names with these layouts! Thank you very much!

[ampdork]

Hey Tony,

I'll dig up my notes later and send anything new your way.

I can say that the clone of this amp I looked at had 470 ohm screen resistors.

I have only seen the 1k5 on the 183 amp.

Interestingly the one I saw had linear taper Level and Ratio pots but on yours I see Aud's... In fact the reason it came to me was the amp seemed to have too much out of the gate with respect to those controls.
I put in 15% aud's and it was much nicer imho...Betting 30% would be even better.

So the original had a deep that was later changed? Also it had a HF taper at one time?

I asked someone once if they felt the amp looked like it had been modified over time but they said it looked to them as if it was built the way it was from the get go....I am back to my own notions that this amp went through an evolution of sorts.

Effing rad layouts Tony. Big ups!!

[dogears]

RF amp had 100k linear pots on both OD controls. Worked just fine that way, as do my three amps with that exact circuit. IMHO, audio taper pots are much worse, and furthermore not what was in the RF amp. Which had a ton of gain! In a good way.....

Shad, maybe super high gain JJ tubes made the audio taper seem warranted? My amps with nice NOS work perfectly with linear. I set the gain at 10-11 oclock.

[ampdork]

Nope I thought it sucked with linears...Sorry but the gain was too damn hot out of the gate...
No JJ's in that amp either. If they once had them in they came that way from the builder.....So wrong tubes then?

This is just my opinion Scott and I noted it as such. I also reported faithfully what was in the amp I saw.

Like I said the amp I saw had linear tapers and I nor the owner dug them...

No idea where Tony got the parts numbers but his layout does show Aud's so I thought it interesting and commented on it.

Either will work, of course, but if one finds the goods cramped up at the front of the pot then an Audio makes more sense (for that person) ....likewise if you get your goods all at the last of the pot a linear would fix it....and if neither does the trick then 30% might get one there...

Not everyone hears things the same I guess. The owner did not dig it and felt it was way too hot and all the good stuff was crammed up in the front end of the pot. I felt the same.

All I did was listen to the client and his amp and changed it to better suit him as the owner. I get it that it may not have been correct strictly speaking but this person is not ford in the flesh.....so if a small change makes that guy feel like he can better nail those tones then i can't see any fault in it.

Anyway like I said linear is what it came with ;O)

[talbany]

Shad
Thanks for the shout out on the layout.. Here is what I found out..

The numbers I have on the pots are correct however were labled wrong.. here are the pot # indicating lin or aud

Volume: 021832 1MEG AUD-1377326
Treble: 021857 250K AUD2-35-13773
Bass: 021857 250K AUD2-35-13773
Reverb: 021873 100K LIN-1377323
Speed: 021865 3MEG-CCWA-1377310
Intensity: 032367 250K-A-1377451

Notice the reverb 100k same as the Ratio/Level indicates Lin
so my bad there and thanks for spotting that..
I can't say where those # came from but know they are accurate the previous info I had on these #'s indicated audio which was incorrect..

Both 183 and the Ford amp in my notes got confusing and read the screens on 183 .. Layout changed..

AFAIK.. The deep switch was removed replaced by mid boost as part of the skyline update like 124.. This is what my notes have if this is different I can gladly change this..

Thanks again and welcome any other info..
Be Well,

Tony

[dogears]

Tony, RF has a 250k linear treble and a 250k 30% audio mid.....

[talbany]

Tony, RF has a 250k linear treble and a 250k 30% audio mid.....

Scott
Thanks for helping out.. Layout revised.. see anything else?

Tony

[UltraHookedOnPhonix]

Tony, RF has a 250k linear treble and a 250k 30% audio mid.....

Scott
Thanks for helping out.. Layout revised.. see anything else?

Tony

I noticed some things on the layout:

-The PS board reads #0124.
-The cap can should read 40/40
-PI Balance trimmer should be 10K

Also, I’ve noticed some conflicting evidence concerning the RF amp:

-Bias feed resistors, I’ve read both 200K and 220K.
-Screen resistors, I’ve seen it reported as 470R and 1K.

[talbany]

Phonix

Thanks for checkin it out..Axe the -124 ..
The Pi trimmer was what was in 124 so I left it..Changed to 10K
AFAIK V1 & V2 are both 40uf.. 2 20's in parallel correct?..I suppose I could label them 40 and hit 1 node?.. Whatever you think

If we find out about the others I'll be glad to switch them

Thanks again!! Rev3 now up..

Tony

[67plexi]

Great work Tony. To cool, The Green Hornet.

Thank you, Steve.

[chris_sanford]

Phonix

Thanks for checkin it out..Axe the -124 ..
The Pi trimmer was what was in 124 so I left it..Changed to 10K
AFAIK V1 & V2 are both 40uf.. 2 20's in parallel correct?..I suppose I could label them 40 and hit 1 node?.. Whatever you think

If we find out about the others I'll be glad to switch them

Thanks again!! Rev3 now up..

Tony

Hi Tony,

Thanks for posting these layouts.. very nice work! Re: the RF... V1B coupling cap is .01? I haven't seen this info posted. Afaik, the usual D value is .047. It would be cool if I'm wrong though.

chris

[talbany]

DOH!!

Thanks Chris!!

Steve looks great Good Luck with it..
Kato

[UltraHookedOnPhonix]

Phonix

Thanks for checkin it out..Axe the -124 ..
The Pi trimmer was what was in 124 so I left it..Changed to 10K
AFAIK V1 & V2 are both 40uf.. 2 20's in parallel correct?..I suppose I could label them 40 and hit 1 node?.. Whatever you think

If we find out about the others I'll be glad to switch them

Thanks again!! Rev3 now up..

Tony

Whoops!!! You're right bout the parallel caps...ignore faulty suggestion.

[Max]

Hi all,

As you all know Robben Ford and Alexander Dumble had and perhaps still have (don't know the current status quo) a close relationship. Because of this #102 was often updated and fine tuned, at least this is what Daved reported.

So I think it would perhaps make some sense before further discussing the details of this layout to decide at first, which stage of the development of the circuit of #102 shall be documented in this layout: 1982, 1996, 2006 or its current circuit?

IMO it would make the most sense to use the current circuit as the reference point for this layout, because Scott obviously has seen the inside of this amp not that long ago, so there is first hand info available and still fresh. So why speculate about what circuit has perhaps been in this amp five or ten or even twenty years ago?

And the original Miles Davis ("King of Priests", "Live in Montreux" etc.) and "Talk To Your Daughter" "classic" circuit of #102 (1982 - at least 1990), is already documented here https://tubeamparchive.com/viewtopic.ph ... 327#137327.

If this new #102 layout shall not represent some kind of "historic mixture" but the current state of circuit and features of #102, I would recommend asking Scott to double check again if the layout now is really in accord with what he found in #102 when he looked inside lately.

Here are some points that may IMO perhaps be worth a double check:

- Really Tandy Wire RG59, as currently in this layout, or the white Teflon coax which usually is a part of all the skyline updates AFAIK? If Teflon, which specs (AWG of the core etc., solid core or stranded core, silver plated copper or silver or copper core etc.)?
- All orange drops 6PS?
- Really a h.f. taper circuit?
- 2.2uF cap connected to terminal 2 of the presence pot really a ceramic disc?
- Which kind of Middle pot? Fender 021857 or Fender 021832?
- Treble pot for sure a linear pot? Which brand and kind of pot precisely?
- PT correct (export?). On some videos, which show the back of #102 and already in the tan cabinet the switch to change the preset voltage is obvious in my opinion
- Really two .01 caps in series between treble pot and rock/jazz switch just as in #124?
- In the "Today you chose.." thread (OP ampdorc) AFAIR there has been some discussion about how to read the snubber values. So are you all sure now that these are 250pF in #102 and not 25pF?
- Speaker outputs: do the two output jacks really have a ground connection done by a wire as shown in the layout? Usually this is done by the chassis material in an original ODS AFAIK?
- V1, V2, V3 voltages?

Some "historic" details:

When RF got #102 in 1982 it will for sure not have been in the black tolex cabinet in which it was mounted in the nineties after its skyline update. This black tolex cabinet obviously has the tolex covered cross bar between the chassis and the grill cloth and this kind of "cross bar cabinet" wasn't yet in existence in 1982. The first amps mounted into such "cross bar cabinets" have been the "classic >>> skyline transition generation goldscript ODS" amps starting around series #14X.

When RF got #102 in 1982 it was one of the very first (#094 was still a transition generation "classic" ODS) 4th generation "classic" ODS amps with a circuit like the one documented in this layout https://tubeamparchive.com/viewtopic.ph ... 327#137327.

When RF got #102 in 1982 it was mounted in a usual 4th generation "classic" ODS cabinet in which it stayed until its skyline mod. Here you can see #102 in a 1989 video at a time when it was still a "classic" amp and still in its original 4th generation "classic" cabinet: http://www.youtube.com/watch?v=Qiz30Hzhta4.

AFAIK Robben Ford's first Dumble ODS #102 stayed a "classic" ODS and in its original Vox grill cabinet until at least June 1990 and then was updated to skyline specs and fitted into the black "cross bar" cabinet.

AFAIK here it is still a "classic", too, and obviously still in its original Vox grill cabinet: http://www.youtube.com/watch?v=eBMC6BHSucY (2:17) and http://www.youtube.com/watch?v=yqn1AnA4CMQ (4:57 and 9:07) BTW: In this concert his 4th generation "classic" #102 is obviously already backed up by his then new backup combination - his goldscript "from classic to skyline transition generation ODS" and a matching tan 2x12" cabinet.

Here in June 1990 this "goldscript" backup amp is still in its original tan cabinet. Later this backup amp (# around 14X AFAIR) was mounted into the green combo cabinet and now it is mounted in the black tolex cabinet. #102 is mounted today in the original tan cabinet of this "goldscript" backup amp.

Here’s a picture of #102 still its original Vox grill cabinet (Miles Davis tour 1986): http://www.gettyimages.com/detail/99638837

Pictures of #102 in the black "cross bar" cabinet and of the "gold script" back up amp in the green combo cabinet you find here http://www.roblivesey.com/dumble/ in the "Robben Ford" link (scroll down a bit until you've nearly reached the end of the series number list).

A picture of the "goldscript" backup amp still in its original tan cabinet you find in the 4th edition of Aspen Pittman's "The Tube Amp Book" on page 154.

Clips of the current circuit of #102 (now in the tan cabinet) are easy to find at the YouTube site.

#102 is the ODS, which sometimes has been called here the "green light, green switches" ODS.

Cheers,

Max