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Fuzzes and NPN Transistors

Started by Natibah, November 15, 2020, 01:32:35 AM

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Natibah

I am building MBP Violenzz and Hipster pedals. I am stuck trying to decide on transistors for these circuits. I have a small selection of NPNs and the hFE reading on all of them are ~280-320. The hipster doesn't say it needs anything specific, so I am guessing that I can just use 2 of the same transistor, the lower hFE as Q1 and the higher as Q2.
The Violenzz says that Q2 needs to be double of Q1. Does anyone know what NPN transistors would be in the 500-600 range?

Transistors I have on hand: 2n3440, 2n3904, 2n5087, 2n5088, 2n5457, bc 183 TI, BC549, MPSA18, bs170, BC407B

danfrank

2N5088 and BC549 may hit hfe of 500 but you really need to get a cheapo meter that can test for silicon transistor hfe, to ne sure. You should be able to get one for $20-25. Unfortunately, transistor gains of a certain part number can be all over the place

Natibah

Quote from: danfrank on November 15, 2020, 05:06:53 AM
2N5088 and BC549 may hit hfe of 500 but you really need to get a cheapo meter that can test for silicon transistor hfe, to ne sure. You should be able to get one for $20-25. Unfortunately, transistor gains of a certain part number can be all over the place
Thanks Dan Frank.
I have a multimeter, which is how I measured the @280-320 range that I posted. I will take a look back at the 2N5088s and BC549s to see if I can find one that gets to 500.

But I imagine I will need to order a transistor and was hoping for a recommendation of transistors that range around 500-600 that would pair with something that I have on hand.

Natibah

#3
Edit: I found my multimeter manual and found that there is a special attachment for reading transistors. So, I will find the attachment and reread my transistors. Please ignore my stupidity.

Original stupidity:
So, this probably belongs in the beginner topics.

I went through my transistors testing all of them for the Hipster build. I narrowed it down to MPSA18 @ 271 hFE, BC549 @ 280 hFE, and 2N3440 @ 340 hFE.

Since the MPSA18 was reading a reverse pinout from the others, I decided to check the datasheet to see if I was reading these correctly (b-e, giving highest hFE). When I looked at the datasheet for each of these transistors, they don't match with what I am seeing. The datasheets say that MPSA18 is a EBC, while the other 2 are CBE; this part makes sense that the one is reverse of the others, but my hFE readings are higher b->c than b->e.

I am also not seeing the hFE readings that the datasheets say I should see. MPSA18: 400-1500; BC549: 100-800; 2N3440: 40-160. 

So I am reading/ doing something wrong. Is anyone able to show me where my mistakes are?
Thanks

matmosphere

Does your meter read huge? If not how are you measuring them?

Natibah

Quote from: Matmosphere on November 15, 2020, 04:19:22 PM
Does your meter read huge? If not how are you measuring them?
Hi Matmosphere, I just found that I am supposed to use an attachment with my multimeter for transistors. I was using the positive probe on the center leg and the negative probe on each side leg to get readings for npn. I believe I read somewhere on the interwebs it was the way to determine the pins, but since my readings are different than the datasheets, I am guessing that the attachment will put them more in line.

matmosphere