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eBay 6SN7 / 300B Amplifier PCB Kit
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6153
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Author:  Woodo [ 16 Aug 2018, 16:21 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

I am concerned about the 450v rating of 47 and 220 uF psu capacitors. I see others use 500 or even 630 v caps here. If not misplaced are there any suggestions for alternatives I could use? I'll check with the local Jaycar as well.

Author:  mwhouston [ 16 Aug 2018, 18:24 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

What is your HT?

Author:  Woodo [ 16 Aug 2018, 22:52 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

The seller recommends a transformer with 320v. After rectification I'm not sure what that will come out at.

Author:  Woodo [ 17 Aug 2018, 18:36 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

Attachment:
6sn7-300b pcb amp-august2018.pdf
[attachment=0]6sn7-3
Woodo wrote:
Please refer to updated schematic - comments welcome. Probably a bit rough.
Slight edit

Author:  Woodo [ 19 Aug 2018, 16:38 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

Added hardware to box. Need to figure how to attach filament transformer underneath but it's smaller holes are narrowing choices.

Author:  Woodo [ 01 Sep 2018, 06:08 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

Plodding away connect wires to the road and chassis. One wire not completely obvious where to put is the the centre tap for the 6.3 volt heaters for the 6sn7's. I read that should connect to ground. Should it go to chassis safety ground in my case? Any advice appreciated. Also there are some white/blue wires on the output transformer labelled "screen" which don't have an obvious place to go. Would that be necessary for a UL amplifier? After that I'll work on how to make 5 volts from the 6 volt winding from the little hammond transformer. Have spoken to a guitar amp guy who offered to help check if it's safe to turn it on once ready. Cheers.

Author:  Woodo [ 01 Sep 2018, 20:16 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

Woodo wrote:
The seller recommends a transformer with 320v. After rectification I'm not sure what that will come out at.

not sure how it works but from reading the posts there is about 40 v loss due to the 5u4g but the rectification of the ac give a dc voltage of root 2 multiplied by that. this gives around 390v dc??

Author:  Woodo [ 08 Sep 2018, 03:40 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

updated pic and first time to put valves / tubes in. the 300bs are from china, the newish 5u4 GB came from northern New South Wales from memory, the 5as4 is an AWA model i bought from a guy in Maryborough, Queensland. i bought some used 6sn7 s of ebay from a USA seller. i got another set of 6sn7s but actually are marked 6h8c and look old and well used. I hope they work! i think they are the same as 6sn7 but will check.

I wish I had the knowledge and fortitude to turn it on safely but i will go the safe route and acquire some help to check things over. thanks for the encouragement so far. regards.

Author:  Woodo [ 08 Sep 2018, 04:20 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

pics as promised. there are a few wires i haven’t trimmed yet. the transformer includes 320 v (used here) and 380v wires. 320v was recommended but i see higher voltages are used in other projects on the forum. There are UL wiring too not used.

Author:  Woodo [ 11 Sep 2018, 16:28 ]
Post subject:  Re: eBay 6SN7 / 300B Amplifier PCB Kit

The recommendations from Matt were followed regarding location of signal ground in the following link.
viewtopic.php?f=9&t=4632&start=50

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