European transistor conversions

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Discussion Overview

The discussion revolves around the conversion of Ukrainian transistor designations (KT835, KT827, KT315) to American equivalents for a device schematic that is reportedly over 50 years old. Participants explore potential replacements for these transistors and discuss the overall design and functionality of the circuit, which appears to be a simple inverter.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant seeks help in finding American equivalents for the Ukrainian transistors KT835, KT827, and KT315.
  • Another participant provides a link to a datasheet for the KT835, but the original poster expresses difficulty in using the information.
  • Suggestions for replacements include using BC337 for KT315, BD139 for KT835, and a general power transistor for KT827, although specific recommendations vary.
  • There is a proposal to replace multiple components with a single n-channel MOSFET for efficiency and reliability, with a specific part suggested (IRL2703).
  • Discussion about the age of the schematic and its relevance, with some participants noting that modern components are generally compatible.
  • Clarifications about the circuit's function, with some participants suggesting it is a simple inverter and discussing transformer configurations (L1, L2, L3).
  • One participant mentions the importance of current-gain for the power transistor replacement and suggests TIP3055 as a possible option.
  • There are questions about the correct wiring for MOSFET replacements and the potential need for additional resistors to simulate base current.
  • Participants express uncertainty about the exact function of the circuit and the specifications of the transformer components.

Areas of Agreement / Disagreement

Participants generally agree that the transistors are outdated and that replacements are necessary, but there is no consensus on the best alternatives or the exact nature of the circuit's function. Multiple competing views on replacement components and circuit design remain unresolved.

Contextual Notes

Participants note that the schematic is quite old, and there may be discrepancies in component specifications. The discussion includes various assumptions about the circuit's operation and the characteristics of the suggested replacements.

  • #31
does anyone know how i can make my own transformer since we can not find one all ready made anywhere. and where i can find those capacitors on that schematic cause i can only find the polarity sensitive one in the bottom center o the board.
 
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  • #32
Those capacitors are commonly available.

If you pull apart an existing transformer, count the turns of wire as you unwind them. Save all the hardware like insulation and terminal connection strips. These might be hard to replace.

Then you can work out a "turns per volt" figure for the transformer. This is often a figure like 3, 4 or 5.
Then calculate the new number of turns for the output voltage you want.

It will be obvious that if you put more turns of wire into the same space, the wire might have to be thinner for it to fit.

Also, you cannot depend on the insulation on the wire to isolate windings from each other. This applies particularly to the mains winding. The best transformers have the mains winding and the other windings on different plastic frames so that leakage between the windings is much more unlikely.
 

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