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10th Nov 2021, 1:16 pm | #81 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Pilot Little Maestro restoration project.
Looks about right if heat sinked properly:
https://www.ohmite.com/assets/docs/acl_hs1.pdf?r=false Lawrence. |
10th Nov 2021, 1:21 pm | #82 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
Jay
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10th Nov 2021, 1:29 pm | #83 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Pilot Little Maestro restoration project.
No problem, my other half used to work for ARCOL at Threemilestone back in the early 1970's.
Lawrence. |
10th Nov 2021, 2:12 pm | #84 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
Chassis has been cleaned up, Still waiting on the dropper parts.
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10th Nov 2021, 2:37 pm | #85 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,741
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Re: Pilot Little Maestro restoration project.
Nice job on the chassis.
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10th Nov 2021, 4:33 pm | #86 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Cheers, Cheapo cleaner from the quid shop
Well iv'e made a start and changed the smoothing caps and audio coupling cap. Not keen on the way iv'e routed the coupling cap wire to the valve base And yea smoothing caps are cheapo china jobs but close to their stated value although the ESR Is a tad high, Old ones have lower ESR But quite a way from their marked values. But thats not too critical in this application. Even a lot of apparently good quality caps these days are fake anyhow. Wee bit of chassis J-Hooking going on too, But my iron ain't big enough for direct to chassis work.
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Help!! I've been electrocuted by a glass thing that glows Last edited by Radio Scotland; 10th Nov 2021 at 4:40 pm. Reason: Correct photo angle |
10th Nov 2021, 5:10 pm | #87 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
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Re: Pilot Little Maestro restoration project.
Those old ones aren't original anyway. They look like Radiospares (RS) 1960's types.
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10th Nov 2021, 5:18 pm | #88 |
Heptode
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Re: Pilot Little Maestro restoration project.
Yeah, Pity the original canned one is gone but frees up space
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10th Nov 2021, 5:32 pm | #89 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
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Re: Pilot Little Maestro restoration project.
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10th Nov 2021, 5:42 pm | #90 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
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Re: Pilot Little Maestro restoration project.
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10th Nov 2021, 5:49 pm | #91 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
Jay
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Help!! I've been electrocuted by a glass thing that glows |
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10th Nov 2021, 5:55 pm | #92 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Pilot Little Maestro restoration project.
Quote:
I don't do PM's anymore. Lawrence. |
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10th Nov 2021, 6:07 pm | #93 |
Heptode
Join Date: Jan 2006
Location: Cornwall, UK.
Posts: 506
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Re: Pilot Little Maestro restoration project.
That's 10W when bolted to the chassis (heatsink), it will be less if it's not; however, it only needs to be more than 2W so that will be fine.
HT resistor calculations: L14 resistance 650Ω L14 voltage drop 202 – 160 = 42V HT current 42/650 = 0.065A Heater current = 0.3A Originally, the total current through the 115Ω section of the line cord between mains and rectifier anode was 0.365A so voltage drop was 0.365 x 115 = 42V (so about 200V at rectifier anode). A 470Ω resistor passing just the HT current will have a voltage drop of 0.065 x 470 = 31V (which is close enough). The power dissipated is 0.065 squared x 470 = 2W |
10th Nov 2021, 6:38 pm | #94 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
Jay
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Help!! I've been electrocuted by a glass thing that glows |
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10th Nov 2021, 6:49 pm | #95 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Pilot Little Maestro restoration project.
The power dissipated by the rectifiers surge limiter resistor will be greater than that calculated using the DC load current figure for I in the Isquared*R formula for power dissipation.
Lawrence. |
10th Nov 2021, 7:53 pm | #96 |
Heptode
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Re: Pilot Little Maestro restoration project.
Over my head i'm afraid lawrence
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10th Nov 2021, 7:57 pm | #97 |
Heptode
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Re: Pilot Little Maestro restoration project.
Ok i'm hoping to get the dropper wired up soon,. Thinking of using some spare tie points on the 25Z4 Rectifier to mount the dropper parts, Ideally pin 6 to heater, Is pin 6 internally connected to the valve ?
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10th Nov 2021, 8:05 pm | #98 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Pilot Little Maestro restoration project.
Quote:
Here's a quick reference to that...2nd sheet then the first few lines in the 2nd paragraph: http://www.r-type.org/pdfs/uy41.pdf It applies to other valve rectifiers as well. Lawrence. |
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10th Nov 2021, 8:33 pm | #99 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Pilot Little Maestro restoration project.
Quote:
Lawrence. |
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10th Nov 2021, 8:35 pm | #100 | ||
Heptode
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Re: Pilot Little Maestro restoration project.
Quote:
Jay
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