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Posts Tagged ‘capacitor replacement’

EICO Stereophonic Integrated Amplifier HF-81 Repair

November 7, 2014 1 comment

From the late ’50s, I had this nice example of an EICO HF-81 amplifier come through my shop. These are nice little stereo amplifiers with a built-in phono pre-amp and RIAA equalization and feature about 14W of power output per channel from a pair of push-pull EL84s each at about 1% distortion.

EICO was a popular brand of electronics kit maker back in the day. They made a lot of hobbyist or entry level shop test equipment (oscilloscopes, generators and testers) but had a handful of hi-fi stereo kits as hi-fi listening grew more and more popular. The fact they were assembled as kits makes them pretty straightforward to service, too – the layout is clean and there’s a lot of room on the chassis. It had been worked on a few times in the past – several coupling capacitors were replaced with early film caps in what looks to be the late ’60s/early ’70s. Just recently, the owner reported it was giving noise from one channel and took it to another local shop where the technician replaced a 50 uF capacitor (orange, bottom left) with a 100 uF cap that looks to me like it was probably an old-stock capacitor (blue, bottom left.) They’d clipped the old cap out of circuit but left its shell intact; not exactly what I’d call a best practice. More problems started cropping up shortly thereafter as the rest of the original capacitors degraded, so it came to me for an overhaul. After replacing the parts, there was still noise,  distortion, and lower volume on one channel seen on the oscilloscope screen in yellow. Tracing through the circuit, it turns out the CRL couplets in the tone network were failing.

I fabricated new PCBs with the same values to replace the damaged parts and mounted them to the shield.

That fixed the problem right up! After some final tweaks and a burn-in test, she’s ready to go home. Lots of parts out of this one:

It’s going to sound great for years to come!

Rain City Audio Tube Audio Repair

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Phase Linear 2000 Pre-Amp Overhaul

October 6, 2014 Leave a comment

Cross-posted from Rain City Audio:

I had a Phase Linear 2000 through my shop lately. It was running okay, but had some pops and clicks and the controls weren’t all that smooth. Time for an overhaul before anything worse cropped up!

This is a pretty fancy pre-amp made to be used with the Phase Linear 4000 power amplifier. It has a variable level output to be paired with a fixed input amplifier.

After fixing it up, I found this one to have a neutral, tight, almost laid-back sound without any extra embellishment. It was very nice – and part of that is owing to the very simple design.

The underside of the single-sided board Quality construction for the era. The bank of switches is an open design which gets gummed up easily but control cleaner easily solved that problem.

Of course, a pre-amp like this deserves nothing but the best: Nichicon Fine Gold series electrolytic capacitors.

The matching power amplifier will come up for service soon, so stay tuned! This Phase Linear is good as new and another piece of gear from the height of hi-fi is saved.

Rain City Audio Stereo Repair

 

Bose 901 Series II Active Equalizer #67402 Repair

August 25, 2014 Leave a comment

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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Check it out at Rain City Audio

1936 FADA 270T Vintage Table Radio Repair

August 8, 2014 Leave a comment

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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Check it out at Rain City Audio

1937 Westinghouse WR 226 Vintage Radio Repair

July 27, 2014 Leave a comment

This 1937 Westinghouse radio was the second highest in their tabletop line-up for ’37 and featured 7 tubes and a large, eye-catching dial for easy tuning. After a full overhaul including capacitors, resistors, an eye tube socket rebuild, new power cord, dial cord re-string, line input addition, and a full alignment it sounds great and pulls in stations across the dial. This model had the alignment trimmers all on the underside which was annoying, but peaked up nicely nonetheless. Read more for photos of the rebuild!

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Check it out at Rain City Audio

1969 GE Model C2504B Transistor Clock-Radio Repair

July 22, 2014 Leave a comment

This iconic late ’60s GE clock radio came to the shop with loud, low humming when turned on and no radio reception. That’s a familiar problem! Time for new capacitors. This particular used a 100 uF main filter and several 200-400 uF secondary filter capacitors around the boards, along with three electrolytic coupling capacitors in the signal chain. They were very tired and as shown by the hum had started to short out; if the radio continued to be run with the loud hum it could have been badly damaged so it came in just in time. Some new components later, she’s good as new and sounds surprisingly good for such a small radio. There’s a mystery switch inside, too – do you know what it might control? Read more for more photos of the repair.

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Check it out at Rain City Audio

Bose 901 Series II Active Equalizer #103549

July 10, 2014 Leave a comment

This Bose® 901 Series II Active Equalizer is a part of Rain City Audio’s parts stock and got a full rebuild with upgraded parts and complete and comprehensive testing. All transistors, resistors, film and electrolytic capacitors were replaced, a new neon bulb added, and the controls cleaned and lubricated. This very detailed repair walkthrough has photos showing the drifted carbon composition resistors which can throw off the equalizer’s curve even if all the capacitors have been replaced. Click through for many more photos!

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Check it out at Rain City Audio

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