Replacement for 2SC657 (Sony)

[deniss77]

The transistor I need to replace is a SONY 2SC657... It's from the AM tuner section of a Sony STR-6045 receiver.

Datasheet from 2SC657 Datasheet. 2SC657 Equivalent, PDF Data Sheets - Parameters and Characteristics. Electronic Component Catalog. gives

Type Designator: 2SC657
Material of transistor: Si
Polarity: npn
Maximum collector power dissipation (Pc): 150mW
Maximum collector-base voltage (Ucb): 18V
Maximum collector-emitter voltage (Uce): 18V
Maximum emitter-base voltage (Ueb): 3V
Maximum collector current (Ic max): 30mA
Maximum junction temperature (Tj): 150°C
Transition frequency (ft): 250MHz
Collector capacitance (Cc), Pf: 2
Forward current transfer ratio (hFE), min/max: 50 (typ)
Manufacturer of 2SC657 transistor: SONY
Package of 2SC657 transistor: U29-1
Application: VHF, Low Power

One replacement I found using Home - Electronics Circuits Schematics TV, AUDIO is BF199, which is available on Mouser:

Type Designator: BF199
Material of transistor: Si
Polarity: npn
Maximum collector power dissipation (Pc): 350mW
Maximum collector-base voltage (Ucb): 40V
Maximum collector-emitter voltage (Uce): 25V
Maximum emitter-base voltage (Ueb): 4V
Maximum collector current (Ic max): 50mA
Maximum junction temperature (Tj): 150°C
Transition frequency (ft): 1100MHz
Collector capacitance (Cc), Pf: 0.6
Forward current transfer ratio (hFE), min/max: 38 (min)

It looks like BF199 has higher power consumption rating as well as higher rated Ic and breakdown voltages... But would I be OK to use BF199 to replace the original transistor, or do I need something else?

[xtechee]

Sub for 2sc657

2sc1923
2sc535
2sc1047
2sc2058s

2sc535 would be the easiest to find, hope this helps.

[Mooly]

If a transistor is used in RF circuitry then substitution can (but not always) be more tricky. The ratings in the data sheet are max values so a device with higher values for voltage, power and current is fine. The real problems come from things such as junction capacitance and gain vs freq. Often you just have to try a suitable device and see how it behaves. You may also have to perform some realignment of any stage the transistor is used in due to differing device characteristics. That could in some cases even apply if you swap like for like.

[deniss77]

Would it help to include a schematic?

The device I'm trying to replace is Q401 in the schematic:

[Mooly]

Q401 looks to be used as a "mixer" taking the input signal and the output from a local oscillator Q405 to produce a fixed IF or intermediate frequency output. It's what is called a "Heterodyne" or more correctly Super Heterodyne receiver.

I think the BF199 has to be worth a try and the only trimmer I would adjust initially would be CT40.

[deniss77]

Originally Posted by Mooly

Q401 looks to be used as a "mixer" taking the input signal and the output from a local oscillator Q405 to produce a fixed IF or intermediate frequency output. It's what is called a "Heterodyne" or more correctly Super Heterodyne receiver.

I found another good possibility:

NTE229
Silicon NPN Transistor
VHF Oscillator, Mixer, IF Amp

[Mooly]

It's not one I am familiar with but seems OK at first glance. This is a case where you are going to have to try them and see.

No one can second guess substitutions like this as the circuit is originally designed around a very specific part, and with it operating at relatively high frequency the device characteristics influence the result even if it can be compensated for via realignment.

That probably sounds a lot worse than it is... try them and tweek just the trimmer CT40.

[deniss77]

Originally Posted by Mooly

It's not one I am familiar with but seems OK at first glance. This is a case where you are going to have to try them and see.

No one can second guess substitutions like this as the circuit is originally designed around a very specific part, and with it operating at relatively high frequency the device characteristics influence the result even if it can be compensated for via realignment.

That probably sounds a lot worse than it is... try them and tweek just the trimmer CT40.

Thanks a bunch! I really appreciate the help and the insight.

[Mooly]

Your welcome and I hope those devices work satisfactorily.

[pshdk]

There is a company in england that have the 2SC657. iso approved, 1 year guarantee. minimum order 130 Euro. I will be placing an order soon if you would like me to get it for you. My order will be more than 130 Euro. Paul