Replace Component in Old Oscilloscope: Solutions Wanted

In summary: I cannot find it in stock on Digikey. I will try to find another dual Fet and put it back to back with good thermal contact.Thanks for the suggestions. I will look into the Jfet and the µA733.
  • #1
Ravaner
134
3
Hello. I have to replace a component at the input of an old oscilloscope. The reference is unfoundable ( 41R105 ? ) in fact it is 2 NFET transistors in the same package (TO-39). I guess Ft is >= 1 GHz. I'm just looking for a component of the same kind (of course not same reference) that iI can find with reasonable difficulties. Thanks by advance for ideas ...
 
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  • #2
Why shouldn't you buy a small lot of single transistors and extract a matched pair through their Vth for instance?

Beware integrated circuits have been made in TO-39, including op amps and HF circuits.
 
  • #3
  • #4
Thanks for your replies. That's probably what I'll do.
 
  • #5
Deeply buried memories...

Last time I considered using Jfet for HF, a good part was the 2N4416, and it's still available on eBay, both in TO72 AND TO92 which should ease a thermal contact between two parts.

I hope you speak sanskrit to read the datasheet, and have kept your tools of reindeer bones and flintstone.

At least a selection guide from National Semiconductor is there, where deepest layers aren't necessarily older:
http://www.alldatasheet.com/datasheet-pdf/pdf/50026/FAIRCHILD/J300.html
the J300 exists on eBay as well, the J300 and J310 being as fast as the 2N4416 with other Idss that may match your part better.

How did you know the component with obscure marking is a double Fet? Back then, the µA733 had a TO39 case as well, and this video amplifier would make sense in an oscilloscope.
 
  • #6
Hello. Thanks for reply. I know pretty well 2N4416 I used in many HF boards ... I know that this is a double Fet because I own the schematics but unfortunately without any component commercial reference
 

1. What is the purpose of replacing a component in an old oscilloscope?

The purpose of replacing a component in an old oscilloscope is to fix any issues or malfunctions that may be occurring in the device. Over time, components in electronic devices can wear out or become damaged, resulting in a decrease in performance or complete failure. Replacing the faulty component can restore the functionality of the oscilloscope.

2. How do I know which component needs to be replaced in my old oscilloscope?

If your oscilloscope is experiencing issues, it is recommended to consult the device's manual or seek the help of a professional. In some cases, the faulty component may be visibly damaged or burned out. Other times, specialized equipment such as a multimeter may be needed to test the components and determine the cause of the issue.

3. Can I replace the component myself, or do I need to take it to a professional?

The answer to this question depends on your level of experience and knowledge with electronic devices. If you have experience with soldering and are familiar with the internal components of an oscilloscope, you may be able to replace the component yourself. However, if you are unsure or inexperienced, it is recommended to seek the help of a professional to avoid causing further damage to the device.

4. Where can I find replacement components for my old oscilloscope?

Replacement components can be found at electronics stores, online retailers, or at specialized electronic repair shops. It is important to make sure the replacement component is compatible with your specific oscilloscope model. If you are unsure, it is best to consult the device's manual or seek the assistance of a professional.

5. Is it worth replacing a component in an old oscilloscope, or should I just buy a new one?

This ultimately depends on the cost and availability of the replacement component, as well as the overall condition of the oscilloscope. If the component is relatively inexpensive and easy to replace, it may be worth fixing the old oscilloscope. However, if the component is rare or expensive, it may be more cost-effective to invest in a new oscilloscope. It is recommended to weigh the costs and benefits before making a decision.

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