Exercise in Crammage---70s 50W ODS in Princeton Rvb. Chassis

[David Root]

Not quite finished yet, but close. 18 1/4 x7". More physical interference issues than anything else. No surprise there! Took my time, still forgot one lead on the board. Can you find it?

This is basically a '67 AB165 Bassman removed and reinstalled in a Mojotone BFPR steel chassis. I paid $250 for the Bassman some years ago, it was not unmolested, so I have a clear conscience.

Added Normster's 97 ODS built in FX loop (V3). Not sure if I need to switch it in/out or not, but provided chassis hole for the switch anyway. So it will be 2x12AX7, 2x12AT7, 2xRCA Blackplate 6L6GC.

It is going into a BFPR combo cab with an Altec 417B, and a satellite Avatar 1x12 w/another Altec 417B. I can't wait!

[guitardude57]

Is that a presence pot wire sitting on the PT?

Nice job on the build!

Did you make the relay board?
I need one that size for my bassman/ods build.
The proto I made (before I was ready) wound up being too big to fit and can't really cut down to size.

[David Root]

Yes it is, just waving about until I solder it down. Made the relay board too. It just barely fits against the switches behind it.

Next time I'm going to find a way to fit the prebuilt relays I have, but they are much deeper than that one.

[gilgalad101]

Are those Riken resistors?

[talbany]

Dave
Looks great!!

Fire it up and post some CLIPS.. Congrats!!!

Tony

[jelle]

Forgot the V1a plate to TSC connection?
Nice build~!

[heisthl]

Beautiful build, bet it sounds good too. - when I read the thread title though, I was expecting some real crammage - you have tons of room left in there - next time do it in a Champ Chassis, with relays for PAB and Mid Boost and also have 2 tubes for Reverb, then you start to approach the maximum "population density" and can claim real crammage.


The 5th preamp tube is buried under the main board.

[CircuitButcher]

David, nice work.

Henry, when it comes to cram, you da man.

Would be great to access the tutorial, Heistand's Cramming Made Workable (cause lord knows it ain't easy).

[ please note: Elmore Leonard has curtailed my use of exclamation ]

[Guitarman18]

Henry,

When 'cramming' like that, which components/layout/lead dress are most susceptible to issues. For example, how close can I put my pre-amp/reverb/d'lator tubes without issues.

Cheers,

Paul.

[David Root]

Sorry, been out of town all this week. Thank you all for your kind words. I have learned a lot about physical layout from this one.

Gilgalad, yes those are Riken CF resistors, mostly 1W. I had a bunch I bought back when they were still in production. They are great resistors, now unfortunately getting too expensive.

Henry you are the Crammer-in-Chief! That's frightening! I would also appreciate some hints as to best ways to prevent/handle parasitics in these crammed builds.

Jelle, the one board connection I know I missed is from the Funky OD Entrance back to the relay. What is TSC? Tonestack cap?

[Structo]

Duncans Tone Stack Calculator.

Nice crammage!

[jelle]

I mean tone stack.

So what does it sound like?! You happy?

[David Root]

That wire is there it's just under the board instead of on top.

I just finished it at 9:00PM last night, so I couldn't play it then, wife's gone to bed...

Later this afternoon I'll bring it up on a Variac, do the usual startup checks, then we'll see what it sounds like!

Just curious, I put in Normster's '97 ODS loop between the master vol wiper (called Level in the '70s model) and the PI input cap. Is this the "normally used" placement of a loop?

I also wired it up per the original connection (at least I think it is) which does not use pin 6 on the relay, instead of the same as #124.

[talbany]

Dave

Thats's correct.. From the master's wiper to the loop back into the PI..You may want to think about a 220K/250pf bypass in series just before the PI as this will help smooth things a bit and help with the loading on the PI..Dumble did this on some like 124 and didn't do it on others.. I like it helps w/ noise too.. FWIW
You also want to wire the OD switching as per 124..This method grounds out the OD when it's in clean channel mode..Quieter and less bleed back using the 124 method..

[David Root]

Thanx Tony, I remember the bypass from my #124 build.

I already wired the relay old-style, just for comparison I'll try it like that then rewire it.

Now all I have to do is get a faceplate and backplate made up.