JapanAxe Posted June 12, 2021 Author Share Posted June 12, 2021 Test fit of eyelet boards (one partly populated) and most front and rear panel components. 6 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 14, 2021 Author Share Posted June 14, 2021 Yesterday was all about metalwork. Most of the chassis hole are now drilled and/or punched. The PT leads will pass through the rubber grommets immediately beneath where it is mounted, but I need to finalise the points at which the OT leads will enter the chassis as they need to be away from the preamp area. 5 Quote Link to comment Share on other sites More sharing options...
Richard R Posted June 14, 2021 Share Posted June 14, 2021 I've been following this with interest. Electronics was never my strong suit, though I still have my battered copy of Horowitz and Hill from Uni days. Quote Link to comment Share on other sites More sharing options...
Hellzero Posted June 15, 2021 Share Posted June 15, 2021 Very neat work ! Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 15, 2021 Author Share Posted June 15, 2021 11 minutes ago, Hellzero said: Very neat work ! Thank you! This time I used a 30mm panel cutter for the valve socket holes instead of a step drill. 2 Quote Link to comment Share on other sites More sharing options...
Mikey R Posted June 15, 2021 Share Posted June 15, 2021 Mert told me you were building an amp from scratch! I'll follow this build with interest! 1 Quote Link to comment Share on other sites More sharing options...
bertbass Posted June 16, 2021 Share Posted June 16, 2021 Following with interest as well. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 25, 2021 Author Share Posted June 25, 2021 I finally drilled the small guide holes that I will eventually widen for the self-tapping screws which will secure the cover to the chassis. I have ordered what I hope will be suitable screws. I also drilled a hole for the safety earth bolt and exposed bare metal around this and the input socket hole using a Dremel-type tool. All the panel hardware is now firmly mounted except for the input socket. It's always satisfying when the valve sockets are in. Next up, a load of soldering. 2 Quote Link to comment Share on other sites More sharing options...
Jabba_the_gut Posted June 26, 2021 Share Posted June 26, 2021 5 hours ago, JapanAxe said: I finally drilled the small guide holes that I will eventually widen for the self-tapping screws which will secure the cover to the chassis. I have ordered what I hope will be suitable screws. I also drilled a hole for the safety earth bolt and exposed bare metal around this and the input socket hole using a Dremel-type tool. All the panel hardware is now firmly mounted except for the input socket. It's always satisfying when the valve sockets are in. Next up, a load of soldering. Really liking this build - it is looking superb. On 14/06/2021 at 22:07, Richard R said: I've been following this with interest. Electronics was never my strong suit, though I still have my battered copy of Horowitz and Hill from Uni days. Crikey - had forgotten about that book from my uni days too! Quote Link to comment Share on other sites More sharing options...
Merton Posted June 26, 2021 Share Posted June 26, 2021 5 hours ago, Jabba_the_gut said: Really liking this build - it is looking superb. Crikey - had forgotten about that book from my uni days too! @Mikey R and I probably still have ours lurking too 🤓 I was always stinky poo at electronics though which is a shame because I’d love to be able to do something like this Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 26, 2021 Author Share Posted June 26, 2021 You may have noticed there are no valve retainers fitted. I did buy ‘bear trap’ retainers but decided not to fit them - the valves will stand above the chassis and the head is for home use only, plus it is a pain to remove valves from bear trap retainers. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 27, 2021 Author Share Posted June 27, 2021 I re-checked my layout this afternoon and found a couple of silly mistakes (plus another after I took the photo). After that I had a bit of a solder session and finished populating both eyelet boards, as well as fitting most of the flying leads, except the connections to the ground bus, which will be made with the boards in place. It's always worth checking component values on a meter before installing them - I found a stray 1ohm resistor in my 220k bag! 4 Quote Link to comment Share on other sites More sharing options...
bertbass Posted June 28, 2021 Share Posted June 28, 2021 Nice! Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 28, 2021 Author Share Posted June 28, 2021 I've now installed the input jack, screened cables, and tone stack board. 3 Quote Link to comment Share on other sites More sharing options...
Jus Lukin Posted June 28, 2021 Share Posted June 28, 2021 (edited) - Edited March 14, 2022 by Jus Lukin Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 28, 2021 Author Share Posted June 28, 2021 7 minutes ago, Jus Lukin said: Looking great so far! This is the fun part! Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 1, 2021 Author Share Posted July 1, 2021 I have now fitted both transformers and made the connections for the mains and HT. The OT primaries are above the chassis at present as they will pass through at a different point. 8 Quote Link to comment Share on other sites More sharing options...
Bassybert Posted July 1, 2021 Share Posted July 1, 2021 Very nice indeed, enjoying seeing the progress of this build. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 2, 2021 Author Share Posted July 2, 2021 14 hours ago, Bassybert said: Very nice indeed, enjoying seeing the progress of this build. I'm always a bit fearful that, when I do my pre-checks and plug an instrument in, I'll be greeted by a tsunami of humming and buzzing. 1 1 Quote Link to comment Share on other sites More sharing options...
Beer of the Bass Posted July 2, 2021 Share Posted July 2, 2021 2 hours ago, JapanAxe said: I'm always a bit fearful that, when I do my pre-checks and plug an instrument in, I'll be greeted by a tsunami of humming and buzzing. Getting the output transformer secondary leads reversed is a fun one - you end up with positive feedback around the power amp (instead of negative), and a loud howl that made my dog hide under the sofa the time it happened to me. 1 1 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 2, 2021 Author Share Posted July 2, 2021 17 minutes ago, Beer of the Bass said: Getting the output transformer secondary leads reversed is a fun one - you end up with positive feedback around the power amp (instead of negative), and a loud howl that made my dog hide under the sofa the time it happened to me. Yep, done that one - only scared myself though! 1 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 3, 2021 Author Share Posted July 3, 2021 Today I made more connections from the transformers to the panel-mounted hardware, added the remaining resistors to the valve sockets, and installed the eyelet board. I ran a copper bus through all the speaker ground connections to make it harder for them to work loose. I have to remember to run another cable from this to the main ground bus, otherwise there will be no ground reference for the NFB circuit. My box of bits is now looking somewhat empty - valves, knobs, feet, fuses, pilot bulb, and a few screws. 6 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 5, 2021 Author Share Posted July 5, 2021 As of last night, all the connections are now made apart form the 6.3V heater supply. The stray white wire is the heater centre tap. 3 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 5, 2021 Author Share Posted July 5, 2021 All the heaters are wired up now. Those pink and purple wires sit well above the audio connections to the valve sockets. I have elevated the heater centre tap by connecting it to the cathodes of the output valves - as I understand it (see Blencowe 3.17), this creates a DC leakage current that is saturated, and consequently unaffected by any AC component from the heaters. All the other bits are now fitted. Time to fire up and plug in - NOT. I'll put this aside and come back to it tomorrow, when I'll check all my connections against the schematic and layout, both visually and with a meter, before running through a staged start-up sequence. I may change my mind about the knobs - I've already done so several times! 7 Quote Link to comment Share on other sites More sharing options...
jimbobothy Posted July 5, 2021 Share Posted July 5, 2021 … very cool, well done 😎 Quote Link to comment Share on other sites More sharing options...
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