Archive for the ‘Repair, alignment’ Category:

2019-06-11 Selenium Rectifier Burned Up, How To Replace

from FB group Vintage Transistor Radios Jun 12 Bob Kirsch has the right idea, but the single replacement diode *must* be rated for 400 V peak inverse voltage or more. A 1N4007 is cheap and readily available. I assume you’re in a country where the AC line voltage is 120 VAC, because the rectified DC

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2019-04-06 HP Transmission Test Set

from FB group Bell Telephone of… Apr 6 (I bought a transmission test set, TTS-4, photo at bottom.) Glenn Peters We had a HP 493something transmission test set for testing up to 56 kb/s lines. I remember seeing the symbols on the green screen, like a carriage return would look like a little ‘CR’. The

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2019-03-19 Radio Alignment Questions

From FB group Building Transistor Radios Mar 20 Bob Kirsch Any recommendation for doing a complete alignment? Documents? I used a HP sweep gen decades ago but I don’t have one now, just an old signal gen. I thought about building a sweep gen but I need to get a few parts. I have bought

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2019-01-27 Replacing Corroded Battery Contacts

From FB group Building Transistor Radios 2018-01-27 Many of the radios I’ve acquired were so corroded that I had to replace metal parts. I used tin can lids to make replacement battery holder contacts. The steel is springy enough to hold cells in place. Scissors can cut the steel, and it can be drilled and

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2018-12-31 Zenith Royal 500 Unique Issue

Also to FB group Building Transistor Radios 2018-12-31 I have several Zenith Royal 500 radios with the ‘long range’ eighth transistor added as a RF preamplifier (chassis number begins with 8). See the attached photo. This does not require a third section on the tuning capacitor, as some ‘TRF’ radios have. Zenith added a tuned

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2018-12-03 My Fluke 75 DMM

from FB group Building Transistor Radios Joe Lima That’s good to hear. More than a year after I bought my Fluke 75 DMM (and with light use at home) I turned the switch to off but it stayed on(!!) I had to unplug the battery. Luckily it was still under the 3 year warranty, so

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2018-11-29 Fixing Badly Worn Volume Controls

from FB group Building Transistor Radios 2018-11-30 I’ve done some experimenting on volume controls that are badly worn and noisy. The idea is to substitute some resistance for the badly worn spot. The loud crackling will be reduced and the normal volume point will be moved to a higher point on the control. For a

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2018-10-26 TV Repair Was A Dying Business

From FB group Building Transistor Radios 2018-10-26 I repaired a lot of old tube TVs, and I saw that the repairs were dying when it was cheaper to remove the chassis from the old TV’s beautiful wood cabinet and buy a new cheap TV and put it into the wood cabinet. It even had a

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2018-10-07 Air Band Radio Kit HMOOABRA_4.3 Part 3

From FB group Building Transistor Radios comment 2018-10-07 Bob Johansen I don’t have a way of calibrating an RF signal level. Back when I worked on Aircraft radios we had General Radio VHF signal generators, attenuators and RF signal strength meters and a Panoramic spectrum analyzer. This would have been a piece of cake to

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2018-08-18 Two Types Of Germaniums In Old Radios

From FB group Vintage Transistor Radios There are really only two types of germanium transistors in older radios. One is for the RF and IF stages and has low collector to base capacitance. The other is audio and can handle a few hundred milliwatts. I recently replaced the germanium audio transistors with silicon, with change

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