2SB525C transistor cross reference help.

[SuperLid]

TIP42 is a drop in replacement.

 

[doffo]

Only if it's a signal amplifier. If it's in a DC circuit, like the bias regulator for the final in a Cobra 2000, not so much.

73

Ahhh! Yep, for sure in a DC Circuit. I was going to buy a lot of 10 TIP42C, but now am afraid I might be buying fakes? Surely TIP42C are common enough that most should be ok? I do see some sets were TIP42 is paired up with TIP41 transistors in lots. I usually buy off eBay. I usually wait to order off Mouse for when I need to buy more Nichicon caps.

The ones I am looking at. https://www.ebay.com/itm/371912485473

***Posted the wrong link, so updated it just now.

 

[SuperLid]

Ahhh! Yep, for sure in a DC Circuit. I was going to buy a lot of 10 TIP42C, but now am afraid I might be buying fakes? Surely TIP42C are common enough that most should be ok? I do see some sets were TIP42 is paired up with TIP41 transistors in lots. I usually buy off eBay. I usually wait to order off Mouse for when I need to buy more Nichicon caps.

The ones I am looking at. https://www.ebay.com/itm/371912485473

***Posted the wrong link, so updated it just now.

Buy from a real distributor. Mouser, Digi-key, Arrow etc.

 

[doffo]

Buy from a real distributor. Mouser, Digi-key, Arrow etc.

Sounds like a plan. I will have it ordered on the next order of capacitors.

 

[loosecannon]

Doffo,

if you compare the schematics, you'll see that this circuit is eerily similar to the AM regulator sections of galaxy and ranger radios that use the 2SB754 (TO-247 style) and the 2SA473 (TO-220).

they are basically the same circuits but the parts were beefed up in the later versions.

so you can replace the 2SA1012 (TO-220) with the TIP36 (TO-247) and the 2SB525 (TO-92) with the TIP42 (TO-220).

the TO-247 would need to be mounted on the chassis wall and as Nomad said, watch out for polarity as the pinouts aren't exactly the same.

Now you have the same circuit that is in the Galaxy radios!

Is this needed? probably not. its more of a "hey why not beef up the parts" kind of thing.
I run my AX-144 this way and have for a few years now.
LC

 

[doffo]

Doffo,

if you compare the schematics, you'll see that this circuit is eerily similar to the AM regulator sections of galaxy and ranger radios that use the 2SB754 (TO-247 style) and the 2SA473 (TO-220).

they are basically the same circuits but the parts were beefed up in the later versions.

so you can replace the 2SA1012 (TO-220) with the TIP36 (TO-247) and the 2SB525 (TO-92) with the TIP42 (TO-220).

the TO-247 would need to be mounted on the chassis wall and as Nomad said, watch out for polarity as the pinouts aren't exactly the same.

Now you have the same circuit that is in the Galaxy radios!

Is this needed? probably not. its more of a "hey why not beef up the parts" kind of thing.
I run my AX-144 this way and have for a few years now.
LC

I think I better replace the two 2SA473 in the President Grant Radio. When I got it, it was missing that 525 transistor and looked like the trace got hot/burnt up. But when you power up, the big 2 watt resistor near the back gets HOT as well as D41 next to the AM regulator/power transistor. I just would rather replace those parts and not chance ruining something else. So when comparing, looks like you can too also use the TIP42 transistors in place of the two 2SA473 transistors?

Thanks for all the help everyone has provided.

 

[sunbulls]

Only after you replaced the caps or other possible components that may have caused the original transistor to burn out in the first place, would I then go with the NTE that you already purchased. It’s easy enough afterwards to test for heat with your fingers. Depending on how hard it’s being constantly driven, it may stay relatively cool. Only if you feel it’s too hot would I place one of the many TO-92 style heat sinks available. Some are mountable, others are free standing. I often choose something free standing to avoid drilling, and the metallic dust that ensues. In either case you will also need heat sink compound.

 

[brandon7861]

If you do use the tip42 as suggested for the SB525, remember that the tab on the TIP42 is the collector. Extending it to the heat sync will require insulating hardware! When it turns on, 8v will be on the tab, so remember its not at ground when you get in there with a scope ground or unprotected probe shield ring.

You could just parallel a couple 625mW transistors if you replace their base leads with resistors.

 

[doffo]

Only after you replaced the caps or other possible components that may have caused the original transistor to burn out in the first place, would I then go with the NTE that you already purchased. It’s easy enough afterwards to test for heat with your fingers. Depending on how hard it’s being constantly driven, it may stay relatively cool. Only if you feel it’s too hot would I place one of the many TO-92 style heat sinks available. Some are mountable, others are free standing. I often choose something free standing to avoid drilling, and the metallic dust that ensues. In either case you will also need heat sink compound.

I did recap the radio. The first thing I did when i got it coming up on 2 years. Just didn't want the nasty surprise of a shorted capacitor.

 

[brandon7861]

Another issue with the tip42 is the current gain. Its Hfe is not >100 like the SB525, its in the neighborhood of 20. Pretty low. Using one there might require a lower value resistor driving the base for it to turn on completely

 

[doffo]

If you do use the tip42 as suggested for the SB525, remember that the tab on the TIP42 is the collector. Extending it to the heat sync will require insulating hardware! When it turns on, 8v will be on the tab, so remember its not at ground when you get in there with a scope ground or unprotected probe shield ring.

You could just parallel a couple 625mW transistors if you replace their base leads with resistors.

I was wondering about that. I would of insulated it from the chassis for sure. Thanks for making sure I remember.