Discussion in 'Tube Audio' started by dcgillespie, Jun 23, 2015.
Thanks! The wood sides are temporary, so I can flip it over. I'm not sure what I'm going to use yet. I've got some maple, cherry, white oak and mahogany scraps. I just can't get to my woodworking equipment in my garage! The last electronics store in the Puget Sound area that I know of is about 30 miles from my house.
Ah. Too bad those are NLA.
I finally had a chance to dial in the voltages yesterday. I ended up changing out the 5 watt 270 ohm resistor with a 5 watt 220 ohm, and adding a 10 watt 50 ohm resistor from the rectifier to the first capacitor. My voltages are now 263v B+, 254v at pin 7, 255v at pin 9, and 143v at pins 1 and 6 on the 12ax7. I used a 100 ohm pot and a 100 ohm resistor in the bias network, and set the bias to 4.9v. Time to build a proper base and figure out what to build next! Thanks again to dcgillespie, Wharfcreek and the rest of the AK community for their help and inspiration!
Finally finished the base, I used walnut with an aluminum strip to match an ELAC turntable I recently picked up. Thanks to Dave, Wharfcreek and everyone else for their help and inspiration on these wonderful little units! On to the next build, this is addicting!
Beautiful job. It's also neat to see someone close to home. I live in Kent and have been working tube amps for a number of years. Not much lately as I'm getting ready to move.
Thanks John, are you staying local in your move? I've got another one of these to build for my brother's friend, then I'm going to finally get to a Pilot 232 I've had on my shelf for about 5 years.
Sent a PM for the personal side of the conversation. On the amp side, do you know if Transcendar is still selling transformers? Nothing at auction and the website shows all the transformer data but can't find any contact info.
I contacted Gery at Transcendar today, he is still building! He says sometimes he gets too busy with orders and basically has to put a halt to new orders. He says he can take orders at this time. Just email him with what model transformer you are interested in and he'll respond with a price. The 7 watt OT's I've been using are TT-234-OT w/o UL taps. $68/ea plus shipping. Send funds via Paypal. I'm not sure if I'm supposed to post commercial stuff, if it's okay to post his email address let me know and I'll post it.
How about you PM it to me?
I'm just up north / across the lake from each of you
Another one joins the ranks, this one is headed to my best friends office. He keeps trying to abscond with my first one, so I agreed to scratch build him one.
Hi everybody. I am attempting my 5th or 6th build. I have mostly built around the original 8601 chassis with the exception of one scratch build. I am currently trying to modify a rca rs-199. I thought I knew what I was doing with the wiring of the ez81 rectifier using the existing power transformer but clearly I am doing something wrong? Just when I think I have somewhat of a grasp of tube audio, I am quickly reminded of my lack of basic knowledge. I am going to include a schematic pic of said transformer and then maybe someone can chime in and tell me how they would wire it to include an ez81. Originally it can be seen it was solid state rectified, but the 330v is obviously too high and I was hoping for a suitable voltage drop from Tube rectification. Maybe this transformer can’t even be used that way?????
You need a center tapped HV tranny. A common cathode tube rectifier won't work with that one.
Yup, you'll need to retain the original voltage doubler configuration for this to work correctly.
Ok, well thanks guys. I learned something new, and I appreciate the help. I rewired it to run as it should but it clearly is making too much voltage. Not sure how to overcome THAT much of an overshoot from what Dave’s schematic calls for so I may just order an Edcor transformer that I know how to work with? I tried bucking the transformer with the extra 6.3v secondary winding but I’m still making 345v with no load.
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