Monthly Archives: April 2016

Dynaco ST-70 Stereo High Fidelity Tube Amplifier

From Rain City Audio: I recently got to work on another vintage stereo kit, the Dynaco ST-70 amplifier. These were powerful, 35W per channel stereo amps typically using a pair of 6L6GC, EL34, or similar power tubes. This turned out … Continue reading

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Bose® 901 Series IV Active Equalizer #265335 Overhaul

From Rain City Audio: This Bose® 901 Series IV Active Equalizer, #265335, just came through the shop for an overhaul. It’s owner bought this equalizer as a part of getting his Bose® system back up and running and sent it … Continue reading

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Bose® 901 Series I Active Equalizer #9724 Overhaul and Upgrade

From Rain City Audio: This rare early-production Bose® 901 Active Equalizer, serial #9724, came through the shop recently for an overhaul. It’s owner reported that both channels would cut out intermittently, the switches were noisy, and the power lamp was … Continue reading

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Bose® 901 Series IV Active Equalizer #223227 Overhaul

From Rain City Audio: This Series IV Active Equalizer, #223227, just came through for an overhaul. The owner reported it wasn’t making any sounds, just providing a DC offset on the output jacks which was giving his power amplifier some … Continue reading

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Dynaco FM-3 High Fidelity Tuner Repair

I recently got to work on a very interesting Dynaco FM tuner, the FM-3, which was in the shop for an overhaul. The owner reported it wasn’t working that well anymore, which isn’t a surprise given it’s age. These are good … Continue reading

Posted in Audio, Electronics, Projects, Radio, Radios and Tubes, Stereo, Vintage | Tagged , , , , | 6 Comments

Bose® 901 Series I Active Equalizer #7790 Repair

From Rain City Audio: This rare early-production Bose® 901 Series I Active Equalizer, serial #7790, came through the shop recently for an upgrade. It’s original owner bought this new in 1969 and kept it in use until it began to … Continue reading

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Bose® 901 Series I Active Equalizer #28322 Repaired

From Rain City Audio: This Bose® 901 Series I Active Equalizer #28322 came through the shop for an overhaul. The original series, these Series I Active Equalizers have the oldest electronic components which are nearly universally out of their service … Continue reading

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