• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Transistor replacement suggestions please.

waggs098

waggs098

Super Member
I'm working on a Philips 7861 that someone else has been in before. They have messed with a few caps and a few transistors.

The transistors in question are Q201, Q202, Q203, Q204. The pics are of the schematic section, and actual board around them.

201 and 202 are labeled as 232-2 NPN transistors.
203 and 204 are labeled as 362-1 FET P - Channel transistors. 203 is completely gone from the board and 204 has one leg broken.

Any suggestions for replacements? Thanks
 

Attachments

  • 20150830_094823.jpg
    20150830_094823.jpg
    55.2 KB · Views: 51
  • 20150830_095919.jpg
    20150830_095919.jpg
    76.4 KB · Views: 56
Register to hide this ad
I can't read , the schematic , to get part numbers .

The two fet's are in the delay circuit , not audio transistors .

the parts lists that lists the transistor would also be helpful
 
The parts list only says what type of transistors they are. NPN silicon or fet p channel and so on. The actual transistor model numbers are on the schematic.

In my orginal post I listed the numbers they give on the schematic for those transistors.

I'll see if I can scan the schematic and get a better copy posted. When i took the pic of the schematic it is very readable until I posted the pic.
 
Those are all nomenclature (parts placement numbers ) not parts numbers , most likely the numbers would be like BC546 , 2N5401 or 2Sk223 on the transistors the others numbers hold no meaning to locate new replacement parts .

What number was written on the Missing FET .
 
Actual numbers on the transistors are as follows:
Q204: 362-1 second line 721
Q202: ST03 second line 200
Q201: 1802 second line N710

I think 204 is an original transistor. According to the schematic 201 and 202 should be the same. One of them has been replaced maybe both. I'm trying to figure out what the originals were so I make sure and put in proper replacements.

Here's.the Philips part numbers if that helps:
Q201 and 202: 610232-0002
Q203 and 204: 610362-0001
 
petehall347 said:
have you got the rest of the schematic ?
Click to expand...

Yeah I have the whole service manual. I don't have a scanner big enough to scan the entire schematic at once. I'd have to post it in pieces. Is there certain info your wanting? I can scan and post that part of the schematic.
 
Last edited:
Anyone know someone who has a 7861 receiver that might be willing to pop the top and see what the original transistors are?
 
hmm...

Got diagram or similar pic? cut an copy paste into a jpg. If somebody has been in before? need a magnifier for new solder and inspect. pull and test? replace xx-rr- your bucks. :D
 
waggs098 said:
Yeah I have the whole service manual. I don't have a scanner big enough to scan the entire schematic at once. I'd have to post it in pieces. Is there certain info your wanting? I can scan and post that part of the schematic.
Click to expand...
was wanting to work out what the delay circuit is for ..
 
ah so it simply shunts preamp signal to ground at power on for a few seconds if i read it correctly .
the fets are basically used as switches ..very little current flowing .
as long as replacements are high enough voltage and current capability they should work .
i would go with something at 30v ish .. 500ma ish ... or higher .
maybe best to see what gate voltages they turn on with by measuring the board ..
the unit should operate with them removed although without the delay . may get a thump .
 
petehall347 said:
ah so it simply shunts preamp signal to ground at power on for a few seconds if i read it correctly .
the fets are basically used as switches ..very little current flowing .
as long as replacements are high enough voltage and current capability they should work .
i would go with something at 30v ish .. 500ma ish ... or higher .
maybe best to see what gate voltages they turn on with by measuring the board ..
the unit should operate with them removed although without the delay . may get a thump .
Click to expand...

Yep you are correct and it did function before I took it apart and there was a pop when it came on. It's completely torn down right now for cleaning and a recap. I didn't even notice the missing transistor until I had it apart. I will continue on it and get it back together then I can measure voltages and see what they are. I was just hoping to find replacements so I could but them in before I put it back together. Really it shouldn't be to hard (for someone with more knowledge then me) to find something that will just do the job since there not in the audio signal.
 
they are sort of in the signal chain ..more of a side chain though ..they don't want to be leaking any DC voltage at all from the gate to source or drain .
 
Almost any P channel JFET should work, though those are not all that common anymore. I am pretty sure Digikey has something, and probably Mouser as well. the specs are not exacting, some manufacturers just use BJTs for that purpose, as long as when turned off, the feed to the base is high impedance.

Nice thing about the FETs is they can do a soft unmute if you like.
 
I found someone at antiqueradios.com that tried something to cross the transistors.
Here's what he did:

"I removed the three zeros from the last part of your numbers, they cross to the following ECG/NTE numbers.

Q201 and 202: 610232-0002 610232-2 ECG/NTE123AP
Q203 and 204: 610362-0001 610362-1 ECG/NTE489"

Looks to me like these should work.
 
Another question. I want to replace the input pair transistors for the amp. If i search using the number on the schematic (83P4) I come up with an NTE159 for a replacement.

If i search using the part number listed in the parts list (610083-4) I come up with an NTE234 for a replacement.

The specs on these are quite different. I'm leaning towards using the NTE159. Can anyone tell me which one I should use?
 
You must log in or register to reply here.
Back
Top Bottom