I have a Heath IG-18 "low distortion" oscillator I modified a number of years ago to become Morrey's Super Oscillator based on a TAA 4/75 article. The IG-18 (or IG-5218) can still be obtained on eBay on occasion and I use mine quite often.
Image Courtesy of The Audio Amatuer Issue 4/75
The large-format file is here:
https://www.ka-electronics.com/Images/j ... llator.JPG (2.3 MB)
A pdf of the article here:
https://www.ka-electronics.com/Images/p ... A_4-75.pdf (5.8 MB)
Morrey's Super Oscillator Heathkit IG-18 Modification
- mediatechnology
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- mediatechnology
- Posts: 5468
- Joined: Sat Aug 11, 2007 2:34 pm
- Location: Oak Cliff, Texas
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IG-18 Modification: What is the Lamp Part Number?
I've always wondered what the industry part number was for the lamp, L1. I recently found this text online at DIY Audio: http://www.diyaudio.com/forums/equipmen ... 8-a-3.html
This is what the original looks like with wire leads:
Image Courtesy of Surplus Sales
The Chicago Miniature Catalog shows that the wire lead, slide base and bayonet base have identical electrical characteristics. Unfortunately they only made 60 or 120V lamps, not 90V.
It would appear that the 90V version had a part number 90PS. Fortunately the 90MB is still made and available:
The original lamp wire lead lamp was either custom-ordered or long-discontinued. I suspect that 90V lamps were used in telecommunications.
Allied Electronics carries the 90MB: http://www.alliedelec.com/search/produc ... KU=9379720
Hope this helps anyone that needs a lamp for their Heathkit IG-18. I love mine.
I'll be ordering some 90MB lamps from Allied and will provide feedback.
I think the 90MB is a replacement based on the following information.The lamp itself is marked SYL 90V. I was able to cross-ref to a Sylvania 90MB, which is a T2 bayonet-mount bulb with the right envelope shape, 90 volts at 30mA, giving a hot resistance of 3k ohms. I pulled one lead of the lamp and its cold resistance is around 280 ohms. I say around because even the small current from the ohmmeter raised it to 290 ohms while I was measuring. This all seems to be in the right ballpark to me, even though the cold R seems low.
This is what the original looks like with wire leads:
Image Courtesy of Surplus Sales
The Chicago Miniature Catalog shows that the wire lead, slide base and bayonet base have identical electrical characteristics. Unfortunately they only made 60 or 120V lamps, not 90V.
It would appear that the 90V version had a part number 90PS. Fortunately the 90MB is still made and available:
The original lamp wire lead lamp was either custom-ordered or long-discontinued. I suspect that 90V lamps were used in telecommunications.
Allied Electronics carries the 90MB: http://www.alliedelec.com/search/produc ... KU=9379720
Hope this helps anyone that needs a lamp for their Heathkit IG-18. I love mine.
I'll be ordering some 90MB lamps from Allied and will provide feedback.
- mediatechnology
- Posts: 5468
- Joined: Sat Aug 11, 2007 2:34 pm
- Location: Oak Cliff, Texas
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