Recent posts

#21

Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A

Last post by nre_admin - Dec 09, 2023, 04:24 PM

Sine wave output at 1kHz and 30kHz.

#22

Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A

Last post by nre_admin - Dec 09, 2023, 04:22 PM

%THD of each channel with new J&J 6BQ5 outputs, NOS Sylvania 6BL8 inverters.  The preamplifier has original Scott 12AX7s (Telefunken).  Amperex 5AR4, old.

<1%THD up to about 10VRMS across 8Ohm NI load.  Input is cross-correlated MLS at 196k sampling frequency.

#23

Vacuum Tube Amplifier Repairs, Restorations and Builds / Scott 222A

Last post by nre_admin - Dec 09, 2023, 04:08 PM

Completed power supply and recap of a Scott 222A.  Some photos of the finished unit.


For this project I resorted to the Hayseed Hamfest 222A capacitor kit to replace the factory multi-caps.  The kits are a bit pricey and if I could find the cans they use would just make them myself.  That said, they do greatly facilitate the cap replacement.  The alternative is installing 16 cans in the already crowded underside.

#24

Direct Radiator Systems / Re: JBL-100 Cabinet redo

Last post by nre_admin - Sep 02, 2023, 06:41 PM

Completed the baffle rework on the Century.  Both the Century and the L-100 were re-oiled, the L-100 baffle was fine.

The Century required new fiberglass lining.  The cabinets are as good as new-make.  Now to install the drivers.

#25

Oscilloscopes, Signal Generators, FFT Analyzers, Multimeters / Re: Tek 465 Power Supply Rebui...

Last post by nre_admin - Aug 23, 2023, 08:15 PM

Well done. Congratulations, the end result is well worth the patience and time invested - that's a nice crisp display.

Thank you!  Having the right tools helps too.
jw

#26

Oscilloscopes, Signal Generators, FFT Analyzers, Multimeters / Re: Tek 465 Power Supply Rebui...

Last post by HD1200xlh - Aug 23, 2023, 09:40 AM

Well done. Congratulations, the end result is well worth the patience and time invested - that's a nice crisp display.

#27

Direct Radiator Systems / Re: JBL-100 Cabinet redo

Last post by nre_admin - Aug 21, 2023, 06:13 AM

The adhesive sheet is very, very sticky and you've got one shot at it.  The roller can be used to "iron out" minor imperfections in the foil, the result is quite acceptable.

#28

Direct Radiator Systems / Re: JBL-100 Cabinet redo

Last post by nre_admin - Aug 21, 2023, 06:10 AM

The foil-cal was removed using a heat gun and very thin stainless steel shim (about 0.010"thk).  The double-sided adhesive is then applied to one side and trimmed.

#29

Direct Radiator Systems / Re: JBL-100 Cabinet redo

Last post by nre_admin - Aug 19, 2023, 03:38 PM

Here's what I plan on using to re-apply the foilcal.




I also purchased a hard rubber roller to assist with the application process.

#30

Direct Radiator Systems / Re: JBL-100 Cabinet redo

Last post by nre_admin - Aug 19, 2023, 03:36 PM

I completed the baffles and re-oiled the veneer using a solution of 1/4 turpentine + 3/4 boiled linseed oil mixture similar to the factory process.

I've removed the foilcal and will re-attach it using a sheet of double sided adhesive from 3M.  I've masked the area where the foilcal is attached and prepped it with 800 grit emery paper.  This will ensure the adhesive has a smooth surface to bond to.