Shorting two of the pins is not an issue, if done correctly. Let's say you have the pot turned all the way to one end. The tricky part is that depending on which pin you shorted to the centre one, you can either have no bias at power up (which is what you want to begin your process) or maximum bias (which is probably not what you want and may release the magic smoke).
I think one reason for shorting one outer pin to the centre is to help minimize the voltage drop across the pots, and leaving more Vds voltage for the jfets. This is more of an issue with higher Idss jfets
I think one reason for shorting one outer pin to the centre is to help minimize the voltage drop across the pots, and leaving more Vds voltage for the jfets. This is more of an issue with higher Idss jfets
I personally verify with a meter, especially the small ones because I find some of the colors on today's resistors hard to differentiate. Not long ago an experienced builder made a mistake on his interpretation of the stripes, causing problems.
Yes, they are, in the schematic.
But not on the bare PCBs from the store. I have 3 PCBs and they do not have a short there.
The short will not remove the pot but it will turn it into a rheostat and in my opinion will make adjustment easier and more predictable.
As Dennis Hui said earlier on, watch out where you solder the short:
Also Post #454:
I pulled the extra shorts off the pots and the New Year’s genie sent me a decent solder sucker today, so I got that power socket off the board (where the little puff of smoke emerged — a first for me) — my guess was that it was flakey. I soldered in wires attached to a barrel power socket, plugged things in, and now I’m suffering through the bias exercise: happy as a clam to have reached this point.
Thank you for your patience and help over the past day. I’m always so cheered by tech communities and how generous they are — my experience for the past 30+ years — and in my slightly different tech world I work hard to pass it on.
Thank you for your patience and help over the past day. I’m always so cheered by tech communities and how generous they are — my experience for the past 30+ years — and in my slightly different tech world I work hard to pass it on.
On to chassis. I've searched and may have missed what I have in mind. Mini needs some protection from/for cats, family members, &c.
This looks interesting, but gosh it's expensive in relation to the Mini: https://partsconnexion.com/collecti.../products/hammond-chassis-cover-model-1451-14
Anyone found an alternative?
Oh, Mini sounds so good, even with my botched bias efforts. Friend will help me with that soon.
This looks interesting, but gosh it's expensive in relation to the Mini: https://partsconnexion.com/collecti.../products/hammond-chassis-cover-model-1451-14
Anyone found an alternative?
Oh, Mini sounds so good, even with my botched bias efforts. Friend will help me with that soon.
Don't laugh, but could something be made from something like this? https://www.ikea.com/ca/en/p/droenjoens-wastepaper-basket-light-gray-blue-40554159/
This is inspired. After several days lost in Ikea, I emerged with no wire basket but some cool wooden boxes and platforms. Fortunately, I was able to subsist on meatballs and sleep in the many attractive model rooms. But it's good to be home.
I agree that it's a shame to cover the amp up. Perhaps that's just not the right thing to do. But I did find these to think about:
Obviously, these would attach on top of a base (slab or box) that the amp is bolted to.
For your top cover, I prefer your second opinion which reminds me of this tube amp from OddWatt
https://diyaudioprojects.com/Tubes/KT88-Push-Pull-Tube-Amp/
https://diyaudioprojects.com/Tubes/KT88-Push-Pull-Tube-Amp/
I just spent an embarrassing number of hours getting the bias approximately right (300mv VB) and was looking for something else and saw this. Thoughts? Also, how close is close enough when setting the bias?
How does your VO look? It's nice to have two DVMs to watch both VB and VO at the same time. It's also nice to have a test point to connect the test leads while making adjustments.