Is dog house too tight?

[Mike_J]

If you looks at the attached pictures you may notice that my doghouse is about 1/16" short in height. I think I have three options. One is to find some shorter standoffs which I don't have on hand. Two is put an 1/8" spacer between the chassis and doghouse where it is screwed on lifting the doghouse high enough to not press on the caps. Third is just screw it down the way it is and smash the capacitors to make it fit.


At first glance option two is looking best to me because I have the spacers on hand. Concern is will the 1/8" gap at the bottom between the doghouse and chassis introduce a noise problem?


Thanks
Mike

[Mike_J]

Fourth options is to remove two star washers from the standoffs. Will make it pretty close doing that.

[Mike_J]

Believe solution four is the option that will work. Removing the star washer gave just enough clearance. Don't think star washer was critical because I still have them at both ends. Lined the inside of the doghouse with electrical tape for a little hopeful added precaution.

[kagliostro]

Other option

Instead of using hexagonal turrets use overlapping nuts (coupled with screws long enough to go from bottom to top) whose total height is lower than that of the turrets

About noise ... I don't think

Remember that electrical tape tends to peel off if the room heats up

better to use a thin sheet of semi-rigid plastic

Franco

[sluckey]

I would just use a blank piece of 1/8" board as spacer. Cut board same size as the cap board.

[mresistor]

I know my True Value carries white plastic spacers in different lengths.. Ace Hardware probably carries them too.   I would get some 1/4" or 3/8" spacers  for the job.

[bmccowan]

This idea will reveal how thrifty I am about reusing materials. Sometimes I make standoffs from short pieces of the outer jacket of a power cable. Works pretty well unless temps get really high.

[Mike_J]

I know my True Value carries white plastic spacers in different lengths.. Ace Hardware probably carries them too.   I would get some 1/4" or 3/8" spacers  for the job.

You are the winner as far as what I ended up doing. Went to Ace and they had 1/4" vinyl spacers but not 3/8". Next closest size was 1/2" which is what I was using but 1/4" will work just fine. Here is a picture of it on the chassis. Have a little more soldering to do but not a problem because I broke out my Weller soldering station which is fabulous. One of my daughter's bought it for me for Christmas. Exact model I wanted.

[Mike_J]

Thank you to all who replied. It was through your suggestions that I came up with an option I am most satisfied with.

[bmccowan]

Looks good - way more expensive than my solution. And, I'm not suggesting you have an error, but be careful on the polarity of those caps if the schematic calls for the first filter to be two caps in series. Its an easy mistake to make - I did it on the first blackface Bandmaster I worked on.

[Mike_J]

Looks good - way more expensive than my solution. And, I'm not suggesting you have an error, but be careful on the polarity of those caps if the schematic calls for the first filter to be two caps in series. Its an easy mistake to make - I did it on the first blackface Bandmaster I worked on.

Two dollars that really didn't need to be spent since it gets hidden under a doghouse but I can't help myself.


I wired the ecaps for the first B+ stage like the original bassman, two 20uF @ 500VDC in parallel. It may have made more sense to install two 100uF @ 350VDC in series with 220K/3W resistors across each cap which I did when I originally built the amp. Don't know if 10uF or 200VDC makes much difference in the tone of the amp but I am trying to make a better sounding amp so I made this change in hopes that it along with some other things will make some difference in the tone of the amp. I am wondering if the AB763 used 700VDC because line voltages went from around 110VAC to 120VAC and 500VDC is pretty close to the edge at current line voltages for the AB763 B+ voltages or the 5f6a I am building for that matter. Not a difficult change to make if I decide to go back to the AB763 style.

[bmccowan]

I can't help myself

Yup - I am a Scot and sometimes I can't help myself from being really cheap. My Mom (RIP) used to balance the old ketchup bottle upside down on top of the new one to drain every last bit. At least I do not do that! Reality is I came to the power cord jacket solution because I was working on an amp, late at night, drinking beer, and realized I had run out of stand-offs. A half-lit Scot is really impatient.
Anyways, I suspect that they did the series filter caps back in the day because higher voltage and higher capacitance caps were either unobtainium or were bulky. I just recapped a blackface Concert and instead of two 80ufs in series used 1 47uf 500V F&T cap. B+ at that cap is just over 400.
I hope you post progress reports.

[sluckey]

Cheap ball point pens make excellent standoffs, especially those old government hex shaped pens. Dremel cutoff wheel makes a quick job.

[bmccowan]

Oh man, Steve, that's a great idea. They also make great bodies for listening amp probes and filter cap drains. A skinny cap like a M-150 will fit right inside.

[sluckey]

This is the pen I was talking about for standoffs. I seem to remember they fit a 1/4" nutdriver.

https://www.amazon.com/NIB-NISH-5062485-SKILCRAFT-Stick/dp/B002JFTR1M/ref=sr_1_12?dchild=1&keywords=skilcraft+white+ballpoint+pens&qid=1610766945&s=office-products&sr=1-12

[Mike_J]

This is the pen I was talking about for standoffs. I seem to remember they fit a 1/4" nutdriver.

https://www.amazon.com/NIB-NISH-5062485-SKILCRAFT-Stick/dp/B002JFTR1M/ref=sr_1_12?dchild=1&keywords=skilcraft+white+ballpoint+pens&qid=1610766945&s=office-products&sr=1-12

Biggest advantage with the pen solution is you can make the standoff any height you want it. However, I don't own a Dremel and since I am also of Scottish heritage that is a problem. Was thinking of buying one though because I want to do a modification to a vertical terminal strip to mount it to the board for a mounting spot for two 68K resistors and a straight wire from the input jacks. Would just need two of the terminals cut down to fit and there would be good isolation from the plate and cathode wires. Additional plus is the 68K resistors would terminate at Pins 2 and 7 of the socket instead of being tied to the input jacks. Don't know that it would make that big of a difference but I have always preferred tying the resistors to the socket. Have a grinding tool with a diamond blade that I am afraid would do the job a little too well. Would probably shred the terminal strip faster than I can blink. With a Dremel I could buy some of those pens and never need to buy another standoff. Guess I will be buying a Dremel tomorrow now that I can think of two reasons for needing one.

[glass54]

Hi Mike
I have a Dremel set but these are also useful. Mini Hacksaw will cut most metals, plastics etc.
You can run the end of pen tubes over some 240 Grade sandpaper to get a nice square/smooth finish. 
I also have a mini Benchvise with suction base, really useful/good for terminating connectors.
Kind regards
Mirek

[PRR]

> I don't own a Dremel

I've always done BIC pen and fine toot hacksaw. Sluckey's SkilCraft seems to be a BIC-like pen made by the blind under a government contract. Glass64's vice and saw are favorites of mine.

[Mike_J]

Hi Mike
I have a Dremel set but these are also useful. Mini Hacksaw will cut most metals, plastics etc.
You can run the end of pen tubes over some 240 Grade sandpaper to get a nice square/smooth finish. 
I also have a mini Benchvise with suction base, really useful/good for terminating connectors.
Kind regards
Mirek

I like this way of thinking. Probably could screw the vertical terminal strip to a board and hack away. I don't have a bench vise, although I have thought many times I should. Don't think I will need one for either of these projects. Need to test fit my board with the vertical terminal strip to see if using the terminal strip the way I am thinking is even feasible. Think I have found the perfect solution. It is the Drill Master 80 piece rotary tool kit at HF. A lot of the 80 pieces are cutoff discs which I think would be a good tool for the job since I am screwing it to a piece of wood. Cost is $9.99. Not much more than the spacers I bought to do this job in the first place. Next I need to buy some of those pens.

[Mike_J]

> I don't own a Dremel

I've always done BIC pen and fine toot hacksaw. Sluckey's SkilCraft seems to be a BIC-like pen made by the blind under a government contract. Glass64's vice and saw are favorites of mine.

Better hold off on those pens as there appears to be a debate as to which is best for the job.

[Mike_J]

Came up with a solution for modifying the vertical terminal strips. Some rusty old nippers I had in the tool box. Made due with what I had available to me. Purpose of the terminal strips is to connect the wires from the input jacks to the 68K grid-stopper resistors. Advantage of these is it keeps the wires high above the board thereby reducing the chance for noise hopefully and to make a solid connection from the grid wire to the grid-stop resistors. Any suggestions for improvement would be appreciated.


Thanks Mike

[sluckey]

IMO it would look neater to run those wires under the board. No noise problems on that end of the board.

[Mike_J]

IMO it would look neater to run those wires under the board. No noise problems on that end of the board.

I was going to try to run the grid wires without shielding. Placing them under the board is going to add length to the wires if they aren't shielded. Another problem I am seeing is the way the terminal strip for Pin 7 is now about 1/2" from the heater wires. Isn't that a potential problem? I have a fix for that one. The top right turret is for an extra 8uF 450VDC ecap exclusively for V1 that is not on Hoffman's board or Fender's either. Pretty sure this is telling me it shouldn't be on my board either. If I move the terminal strip into the location that ecap would have been in then problem solved. Running above the board to the terminal strips would be about 3-1/4", excluding length for grid-stop resistors which would probably add another inch. Would need to add at least 2" more to run it under the board. Do you think I would need shielded wire once I get to that point?