2N5485 alternative (muffler)

[skunk]

I'm building the muffler pedal and Q3 requires a 2N5485 transistor. These have become extremely difficult to source (UK) and I don't want to risk spending a bunch on ebay for something which could be fake. I've had a search around a few sites and there's been a few people asking for suitable alternatives to the 2N5485 (MMBF4393, NTE451, PN4393) but I haven't seen anything definitive. The few alternatives I have seen mentioned are generally just as rare/expensive these days too.

Are there any readily available replacements I can use instead?

 

[temol]

Here are measurements taken from actual transistors (5 minutes ago...)
Model - Vp/Idss
MMBF5485 - 2.66V/6.40mA
MMBF5458 - 1.75V/3.6mA
MMBF5457 - 1.57V/3.22mA
MMBF4393 - 1.96V/1.43mA
MMBFJ201 - 0.72V/0.52mA

 

[MBFX]

I'm also having this problem. Is the MPF102 a suitable substitute?

 

[Mcknib]

I'm also having this problem. Is the MPF102 a suitable substitute?

MPF102 should be fine Gpcb has 5485's if you want them

JFET 2N5485 - For Sabotage PCB - GuitarPCB

2N5485 - Guaranteed Genuine Limited supply from my personal collection.

guitarpcb.com

 

[Laundryroom David]

MPF102 should be fine Gpcb has 5485's if you want them

JFET 2N5485 - For Sabotage PCB - GuitarPCB

2N5485 - Guaranteed Genuine Limited supply from my personal collection.

guitarpcb.com

Guitarpcb is a trusted source. Never had a bad component from Barry

 

[MBFX]

MPF102 should be fine Gpcb has 5485's if you want them

JFET 2N5485 - For Sabotage PCB - GuitarPCB

2N5485 - Guaranteed Genuine Limited supply from my personal collection.

guitarpcb.com

Thanks!!

 

[DeadAirMD]

I second what @Laundryroom David said about Barry at GPCB, never had a bad part. Just stocked up on a bunch of j201's. Wish he still had j113, I got one of the last orders from him when they were available.

 

[Mcknib]

Guitarpcb is a trusted source. Never had a bad component from Barry

Aye I'm in Scotland and I get all my through hole fets from Barry boy it's a lot cheaper than getting them in Europe + I know he tests every single one he sells

 

[MBFX]

I ended up ordering some MPF102s from Amazon for cheap, as well as some 5485s from GuitarPCB, because I am impatient and wanted to futz with the pedal today. In the Muffler, an MPF102 works in place of a 2N5485... kindof!

The threshold and clamp aren't quite right. The threshold is very sensitive and has an extremely narrow range in which it clamps a signal effectively. If you set it even a tad too high nothing passes at all, and there is a small range above that where you get a weird dying-battery effect where the gate doesn't quite close and the signal sputters. Above that in the useful range the gate passes a very small amount of signal, but maybe the pedal "just does that" - I only own a Revv G8 and an ISP Decimator, so I am used to a perfect clamp and base my experience on that. Above the useful range where the guitar signal itself prevents the gate from clamping, you get a little treble boost. Weird!

I have a bag of 25 more ICs and 9 more JFETs. Both are Chinese from Amazon. Should I try auditioning more chips, test the rest of my JFETs and solder in the one with the best value (which maybe someone could help me determine?), or wait for the proper JFETs to arrive from GuitarPCB and report back when I have one in?

 

[MBFX]

I received my JFETs from GuitarPCB, but something is wrong. None of them test correctly on my TS1 multifunction tester - they test as a resistor or an inductor depending upon orientation. Other transistors test fine, and the tester does do FETs. I installed one to see what would happen, and there is no gate. Just a clean signal! Not sure what is wrong, but I know it isn't my soldering or wiring as the only thing I have done is swap an MPF102 for the recommended 2N5485.

Any ideas?

 

[Laundryroom David]

I received my JFETs from GuitarPCB, but something is wrong. None of them test correctly on my TS1 multifunction tester - they test as a resistor or an inductor depending upon orientation. Other transistors test fine, and the tester does do FETs. I installed one to see what would happen, and there is no gate. Just a clean signal! Not sure what is wrong, but I know it isn't my soldering or wiring as the only thing I have done is swap an MPF102 for the recommended 2N5485.

Any ideas?

Pinout?

 

[MBFX]

Pinout?

The MPF102 and 2N5485 have identical pinouts, and the board helpfully illustrates the correct orientation. Pinout is also irrelevant to my tester; diodes and transistors can be oriented either direction and the tester will identify SDG (or CBE, or directionality). It doesn't make sense that the whole bag of JFETs doesn't register as any kind of transistor, but rather only an inductor or a resistor depending on orientation.

I have heard JFETs are inherently not good. Did I get unlucky and receive a bag of bad parts? My MPF102s all test correctly, and the two I have tried work (kindof) in the circuit.

EDIT: I highly doubt I actually got a whole bag of bad parts. I'm just stumped and don't know what to test next. Does anyone have any recommendations on how to test a JFET with a multimeter? I'm very good at soldering and stuff, but I know very precious little about transistors

 

[temol]

Are you sure that TS1 correctly identifies the JFETs? Try other methods, described here (bottom of the page) or here.

 

[MBFX]

Are you sure that TS1 correctly identifies the JFETs? Try other methods, described here (bottom of the page) or here.

I really, really appreciate those links, as well as your question about the tester. I shouldn't have trusted the manual - while it can apply a negative source voltage, it looks like it can only supply about 5VDC. If my understanding is correct, that isn't enough to open the gate and will explain the bad result. Can you confirm?

I will read through those docs you linked more thoroughly when I'm not on my lunch break, and see if I can determine what the problem is.

 

[Mcknib]

I use a DCA75 those testers aren't the most consistent

I've got one and you definitely have to put the pins in the correct row / numbered socket or you'll get strange results I think certain slots are for diodes etc

Did you do the calibration procedure

TC1 users, some questions for you

I just ordered a TC1 tester--my intent was to get ballpark measurements for some Ge transistors. I'm pretty frustrated with it though: I'm finding it doesn't detect JFETs, it doesn't detect Ge transistors, and it can't measure detect several types of high-gain BJTs (I'm getting no readings on...

forum.pedalpcb.com

 

[MBFX]

I have solved my problem! It was, in fact, bad JFETs. I ordered some SIP snappable sockets, socketed the 2N5484, and tried them all, including the one I removed. The one I removed was bad (barely clamped), 5 others in the bag were bad (1 no clamp, 4 barely clamped), 3 worked alright (would quiet down a dimed Distortion +), and one worked really well (I can stack a loud phaser with the Distortion + and get a good volume reduction).

Since GuitarPCB is a reputable source and everything I'm reading says this is a common occurrence with JFETs, I don't think any fault lies with GuitarPCB. The transistors might even work fine for other applications - I'll find out next time I need one!

 

[temol]

I really, really appreciate those links, as well as your question about the tester. I shouldn't have trusted the manual - while it can apply a negative source voltage, it looks like it can only supply about 5VDC. If my understanding is correct, that isn't enough to open the gate and will explain the bad result. Can you confirm?

I will read through those docs you linked more thoroughly when I'm not on my lunch break, and see if I can determine what the problem is.

I have never tried to find the reason why there are problems with measuring some JFETs. It is possible that it is as you wrote - too low voltage/current. Either way - I prefer simple measurement with DMM.