dorrisant wrote:If you do the stack of caps you can just slide the stack a little toward the back of the chassis before you secure them. This should get you enough room for the VVR.
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Keep in mind... You can probably mount the pot separate from the board so you can get the control to the front panel our wherever.
M Fowler wrote:What your dealing with is rather common these days two PT wire holes not one. Plan ahead and proceed.
Ok. PT, OT and other mechanical bits installed. I am now able to plan for the VVR and stack-o-caps.
It appears that with my PT having 2 looms of wire rather than 1 I have a conflict with the caps anyways even without the VVR... I will need to either move the caps really forward or do something quite different. I am not sure how the amp will behave if I need to move the caps as forward as I seem to need...
Has anyone tried installing the caps on top of the chasis similar to Fender installs?
You use smaller physical size cap or one of the Brothers Hall used a pair of can caps on one of their builds.
I use smaller caps rather then the large Mallory TC caps which work really well in the larger confines of the Rocket but not so well with Express/Liverpool.
Maybe your power board should have been raised slightly and cut around the MOV and power switch to fit tighter.
Mark
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Thanks for sharing your photo and some ideas. I think the least deviant solution I can come up with could be to swap the position of the 20uF caps with 40 uF caps. The 20Fs being smaller will fit better in the lower row and there will be more room for the 40 uFs up above. Let me do the scoping...
Other option is to elevate my PT a little on top of the chassis by way of spacers and then route back the 2nd loom of wires so that all wires go through a larger single loom as in the originals...
Ok. I think I'm going with this approach. Seems to be the least impactful. I installed the VVR board next to the pot. Some countersinking on the front panel gets me there nicely. Then the small caps go first floor and large caps make up the second floor... Overall they are moved forward less than half an inch. See my photos for some critique. Do you think this approach might cause noise & mayhem? Thanks for your input.
For some strange reason I don't have any gut shots of my Express.
But one thing that can be done is move the tone board as far over as you can to make room for the Mallory cap stack.
Your PT and OT seem to be positioned correctly so that cannot be the issue.
Just that the PT wire hole is in the way.
Top photo is Richie Hall's amp with can caps.
Bottom is my Express PT/OT positioning. Note my tone board machine screw heads are right at the left edge giving me as much room as I possibly can get.
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The preamp board in my express is right up against the input side of the chassis. I used the Sprague caps which are big too. Make sure you condense the stack as tight as possible so you are still able to put the bottom cover plate on the chassis.
MCK wrote:Drilled new holes. Now it looks like it will fit but the height of the overall cap stack is a concern as you point out.
They should fit, sometimes the tranny bolts can be an issue if the are in the way. If so you can bolt them from the bottom if that is the case so the screw head fits under the cap stack. I did that on my express...I have gut shots but not on this computer...I have a build thread I will see if i can find it.
My head is about to explode. I am populating the boards and trying to figure out the small changes required to the preamp board to accomodate the VVR. Referring to the following thread where Dana provides info on this topic :
The board that I have already has the extra turrets for this mod but I don't know if I have the correct caps at hand. Can anyone kindly comment on the values they used that worked well? Thanks much!
Assuming you are refering to the additional caps to keep DC "in it's place", the rule of thumb is to size the caps equal to those between the PI and power tube grids. 0.022 uf for an Express.
Note that this is a low voltage application so ~50V to 100 V rating are acceptable...and...physically smaller than our typical full voltage coupling caps.
I played around a bit with these in my VVR implemented Express'ish build and, to my ear, a 0.10 uf sounded the best. As always...YMMV.
Great input. Thanks much for that. I am moving slowly populating the boards taking care not to make a mistake. Will post when they are both done.
Thank you very much for all your help TAG community. You are the best. Wishing you all a very good 2012. May you and your families have the best of health, happiness and prosperity. See you in 2012!
Quick follow-on question on VVR related cap & resistor changes... Referring to the gut-shot Dana posted in the linked thread above, he seems to have removed the 1k5 resistor identified as R2 which is parallel to C1 (22uF) electrolytic cap which can still be seen there. How does this work? I understand I need to add the 1M resistor there but I don't understand why R2 is not there.
It would be amazingly helpful if I could see an Express schematic showing these cap & resistor changes. I have read all posts since 2009 when Dana introduced the VVR but I did not come across an updated schematic showing VVR integrated. Does anyone know of one?
I attempted to put my understanding and confirmation question into the schematic. Can you kindly take a look at the attachment and let me know if I am getting this right? Apologies for being such a dumbo.
Thanks much as always! Have a great Jan 1st!
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If any one with VVR installation experience could take a look at the schematics I tried to update above and let me know if I'm on the right track I'd appreciate it immensely. Thank you very much for your time. Keep well.
