Monthly Archives: August 2014

Bose 901 Series IV Equalizer #202245

A bit different from the run of Series I and Series II that I usually see, I got to fix up this Bose 901 Series IV Active Equalizer which was sent to me from Austin, TX. The Series IV was sold from 1978-1983 and its construction reflects this.

The PCB on this model is single-ended, so can be completely removed from the chassis.

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Bose 901 Series II Active Equalizer #67402 Repair

This equalizer got a full overhaul with new 1% precision resistors, electrolytic capacitors, audiophile-grade output capacitors, transistors, gold-plated RCA jacks, 4% silver solder for all connections, a thorough switch cleaning, and computerized frequency response testing and a listening burn-in to verify proper operation. It sounds just fantastic with a very dynamic and life-like presence that really draws you into the experience of the source material, just like the Bose 901 should.

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Wanted: Vintage HP 1400-Series Vertical Amplifier Plug-Ins for Oscilloscope

I’m looking for plugins for my HP 143A Wide-Screen Mainframe Oscilloscope which I’m in the process of restoring. I’d love to run it as a 15″ high speed X-Y display, and to do so needs matched vertical amplifier plugins in … Continue reading

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1930s Vintage Detrola 335 Radio Repair

Repairing this Detrola 335 was a major detective project with only a partial schematic after it was hacked on was a major project, but this radio cleaned up nicely and came back to life after tracking down all the faults, including replaced components, undocumented modifications, and a failed thermal switch. After adding an eye tube per the owner’s request, this fantastic art deco style tabletop radio is going to play beautiful music for many years to come. Click through for many more photos and schematic snips of the repair process!

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New Toy: HP 143 Wide-Screen Oscilloscope Mainframe Restoration – [Part 1]

At the risk of becoming a test equipment collector, I am picking up a few pieces of vintage test equipment that need some work, but will be very useful pieces of shop gear as well as interesting pieces of history … Continue reading

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1936 FADA 270T Vintage Table Radio Repair

This FADA 270T radio which came through the shop lately was a beautiful, very high end radio back in 1936. It has a huge airplane dial with dual-speed tuning and a magic eye indicator, and a beautifully organized under-chassis layout. Repair was pretty straightforward with a few surprises at the very end, but nothing that couldn’t be fixed. Click through to read more – there’s dozens of detailed, colorful photos of antique resistors and the magic tuning eye.

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Close-Up of a Magic Eye

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1959 Zenith C845M High Fidelity AM/FM Radio

This radio repair is cross-posted from Rain City Audio

This classic 1959 Zenith C845M radio came into the shop for a full repair after sitting unused for some time. It has the classic late ’50s styling, and a dual speaker high-fidelity design.


It’s an 8-tube radio with a 35C5 output tube good for maybe 3W of maximum output, but it has great sound quality.


Inside, it’ Continue reading

Posted in Hi-Fi, Radios and Tubes, Vintage | Tagged , , , , , , , , , , | 7 Comments