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Recent posts
#91
Horn Loaded Systems / Re: B&C DCM50 w/Selenium HM359...
Last post by nre - May 29, 2023, 10:46 AMThe baffle insert was compared to the Klispchorn unit and evidenced a significant improvement.
#92
Horn Loaded Systems / B&C DCM50 w/Selenium HM3590 Bi...
Last post by nre - May 29, 2023, 10:43 AMNot sure why this combination isn't more popular with the Klipschorn modifications folks. The horn has a specified Fc of 400Hz and, based on the on-axis response plots the compression driver works well into it. The plots clearly show the driver is working into a reasonable radiation resistance to about 350Hz making the combination suitable for pairing with bandwidth restricted Klipschorn bass unit. FWIW, it blows the stock unit away, mids are crystal clear (no "shout").
Here's the plot of the mid-horn without a filter (green) and with a 400-6000Hz band-pass (gold).
Plot below shows the on-axis response of the mid-horn (gold) and tweeter unit. The green response is the integrated response of the two.
Here's the plot of the mid-horn without a filter (green) and with a 400-6000Hz band-pass (gold).
Plot below shows the on-axis response of the mid-horn (gold) and tweeter unit. The green response is the integrated response of the two.
#93
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by nre - May 29, 2023, 09:52 AMCaps installed.
There are two types of Orange Drop capacitors made by CDE (the originals were made by Sprague). Use the 715P type which are Polypropylene.
There are two types of Orange Drop capacitors made by CDE (the originals were made by Sprague). Use the 715P type which are Polypropylene.
#94
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by jwarren_NRE - May 22, 2023, 05:56 AM #95
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by jwarren_NRE - May 21, 2023, 06:33 AMThe American Radionics 0.1uF are to be replaced with polypropylene films. The CDE orange drops are fine for this application.
#96
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by jwarren_NRE - May 21, 2023, 06:11 AMMulti-caps replaced, power supply for -55VDC filament string replaced. All resistor are ceramic composition, non-inductive consistent with carbon composition.
C201
C203
C202
Filament string:
Things are now looking much better!
C201
C203
C202
Filament string:
Things are now looking much better!
#97
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by nre - Apr 30, 2023, 05:25 AMThere are sources for multi-cap cans, CE Manufacturing fabricates them in a manner similar to Mallory, they claim they're identical. Hayseed Hamfest stuffs new cans using discretes and they sell a set specifically for the 222C/D.
When prepping for a replacement can, twist the locks back and wiggle the can free. If the insulator cracks you'll need to replace it and that means drilling out the rivets. The rivets can then be replaced using fasteners.
When prepping for a replacement can, twist the locks back and wiggle the can free. If the insulator cracks you'll need to replace it and that means drilling out the rivets. The rivets can then be replaced using fasteners.
#98
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by nre - Apr 30, 2023, 05:16 AMSelenium rectifier must be removed and replaced with Silicon, 4A.
#99
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222C
Last post by nre - Apr 30, 2023, 05:11 AMThe multicaps, all, must be replaced.
C201, 202 and 203.
C201, 202 and 203.
#100
Vacuum Tube Amplifier Repairs, Restorations and Builds / Scott 222C
Last post by nre - Apr 28, 2023, 06:09 AMThis unit came in a couple weeks ago, a 222C.
The owner has had problems with having it service by others. It was very dirty with years of dust accumulation. The unit is, based on my initial look, all original. The underside does not appear to show any rework by others.
Pulling all tubes, replacing the rectifier with a solid state plug-in and bringing the B+ to 420VDC reveals problems. So first thing will be to replace the multi-caps, the germanium bridge rectifier with silicon.
And before you begin working on the amplifier attach a grounding strap that ties back to the Earth lead at the box and check the fuse. All Scott amps use 2.5A slo-blows. The one in this unit was 12A(!!!).
The owner has had problems with having it service by others. It was very dirty with years of dust accumulation. The unit is, based on my initial look, all original. The underside does not appear to show any rework by others.
Pulling all tubes, replacing the rectifier with a solid state plug-in and bringing the B+ to 420VDC reveals problems. So first thing will be to replace the multi-caps, the germanium bridge rectifier with silicon.
And before you begin working on the amplifier attach a grounding strap that ties back to the Earth lead at the box and check the fuse. All Scott amps use 2.5A slo-blows. The one in this unit was 12A(!!!).