[CharlesParticipant]

I just picked up an old Raytheon  Series 3 set on eBay, which I believe is the same series as the one I had when I was 10 years old. It looks like the 100K transistor has failed in the set. My diode tester shows continuity both ways base to emitter, so I assume it’s shorted. What’s a suitable replacement transistor that is easy to obtain?

Thanks, Charles

• This topic was modified 4 years, 8 months ago by Michael.
• This topic was modified 4 years, 8 months ago by Michael. Reason: Changed font and size styling for easier reading

[MichaelKeymaster]

Hello Charles and welcome!

I have written to you under separate cover concerning a replacement block.

Nevertheless, it would be helpful to know what the appropriate transistor replacement would be.  Our two resident Lectroneer experts – Günther and Frank – may be able to answer this question.

Please feel free to add additional topics and questions!

We would all like to know more about your earlier experiences with the Lectron System.  Your recollections using the Raytheon Series 3, how it perhaps influenced your professional career choice, shared time with family members and especially if you have any early photos of you playing with the Lectron System would be really great.

Best regards,
Michael

• This reply was modified 4 years, 8 months ago by Michael.

[LectronFanModerator]

Hello,

The transistors used in the legacy Lectron sets are made from Germanium, which is completely different from the types made of Silicon we are using nowadays.

If you want a replacement for these Germanium (Ge) transistors, you need to check if they are PNP and also the right type.

For example, the AC125 is a Germanium (A) and a low frequency  audio amplifier (C) type.

Please be aware that those transistors are obsolete and the price for new old stock can be quite high.

I don’t have my comparison chart right now but I’ll look it up when returning home from holidays.

These are European types of transistors, so I don’t quite know the American equivalents.

I do have a local firm which has these AC125 transistors in stock, so if you’re interested I can contact them.

Many greetings,

Frank

• This reply was modified 4 years, 8 months ago by Michael. Reason: Changed font and size styling for easier reading

[MichaelKeymaster]

Thanks for the details and your counsel Frank!

Best,
Michael

[GuentherParticipant]

Hi all,

as the long year semiconductor administrator of http://www.radiomuseum.org I can offer to visit this homepage, click the “country flag” to choose your favourite language, select the tab “tubes…” and enter AC125 in the input field.

Because of my yesterday upgrade to Win10 all is new for me and I don’t find the snapshot tool yet, so I did it with my good old IBM OS/2 and Firefox in my language:

All the blue and underlined types (and many more…) may be used as an equavalent. Below are some known data of the AC125. It’s a standard AF amplifier germanium PNP transistor, so it should be no problem. I have several of this in among my spare parts, so I could send it (only shipping cost) to you.

This Lectron transistor blocks sometimes failed because of bad handling and wrong connections, so it’s good to have some transistors for repair…

Wish you success!

Best,

G.

• This reply was modified 4 years, 8 months ago by Michael. Reason: Changed font and size styling for easier reading

[MichaelKeymaster]

Thanks so much for these helpful details Günther!

[CharlesParticipant]

Turns out that it’s not too hard to find NOS AC125 transistors. They were used in a 1960’s era guitar effects pedal called the Fuzz Face. If you’ve ever heard any Jimmy Hendrix, you’ve heard a Fuzz Face. The original version had two NKT275 germanium transistors, which is very similar to the AC125 (in the list above, in fact). The germanium transistor was very sensitive to temperature and the sound would change as the temperature varied, so later models went to silicon transistors, but those just don’t sound as good to expert guitar players, so many players modify the modern units to use germanium transistors and the transistor of choice is the AC125, so there are many places that have acquired old stock and sell them at a reasonable price, often in matched pairs. I picked up a pair on eBay for about $10 with shipping.

Since Michael is generously sending me a new block and if I can fix this block, it would be interesting to see if I could build a Fuzz Face with the Lectron blocks. It’s just a simple two-transistor amplifier, though I would need more resistors, one more capacitor, and the potentiometers are different.

Sometime in 1968 I saw an advertisement for the Raytheon Lectron set. I don’t recall where, but we were subscribing to Popular Electronics at the time. I’m sure I was rather a pest about it and it was under the tree on Christmas morning in 1968. I was nine years old. My most distinct memory of that time was building the oscillator circuit and my dad explaining how an oscillator works. I’m sure I built everything in the book many times. I had the set until college, but lost it somehow moving around at the time.

I always knew I wanted to work with computers. I started in Electrical Engineering in college, but switched over to Computer Science. I worked in both hardware and software over the years, but haven’t done much hardware in a long time now other than as a hobby. I’m now a Computer Science professor at Michigan State University.

I have two young grandsons. Luke is 5 now and it won’t be long before I can introduce him to the wonders of electronics.

I love the technologies of the 60’s. In addition to the Lectron set, I have a DEC H-500 Digital Logic Lab. I would love to know what that thing cost in 1968 when it was built. I also have an EAI TR-20 Analog Computer that I restored and which is completely operational.

Charles

• This reply was modified 4 years, 8 months ago by Michael. Reason: Changed font and size styling for easier reading

[MichaelKeymaster]

Thanks Charles, 
Your back story is very interesting.  I always enjoying learning how the Lectron System was a part of generating interest and passion for electronics.  How wonderful that you will use it to introduce your grandsons to electronics!

[LectronFanModerator]

Hi Charles,

Thank you for your Info ! Hopefully you’ll get a lot of fun with your Raytheon set and that you’ll post some pictures !
If you would share the circuit of the fuzz amplifier, I’d love to help you converting this to a circuit which uses the standard Lectron values.
Have you also checked the amplifier circuits in this forum ?

Regarding the digital DEC H-500, I found a website with lots of info and a pdf of the user manual. Here is the link.

It’s not quite Lectron but may give some inspiration for Lectron circuits.

Greetings

• This reply was modified 4 years, 7 months ago by LectronFan.
• This reply was modified 4 years, 7 months ago by Michael. Reason: Changed font and size styling for easier reading

[CharlesParticipant]

It works! Thanks Michael!

I had the manual for the H-500. What I would like to find is a schematic, though right now it is completely working.

• This reply was modified 4 years, 7 months ago by Michael. Reason: Changed font and size styling for easier reading

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