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Old 25th March 2005, 02:18 AM   #1
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Default I need help identifying MOSFETs

I have a Hafler P500.
It is missing 3 of it's MOSFETs. They are labled;

OP113 and QN113. Does anyone know who makes/made those?

If they are not made anymore, do you know of a replacement?

Thanks, Terry
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Old 25th March 2005, 03:58 AM   #2
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http://www.profusionplc.com/exicon.htm
http://www.profusionplc.com/hitachi.htm

Original Hitachi 2SK176 = QN 113 for your DH-500
Original Hitachi 2SJ56 = QP 113 for your DH-500

Profusion (Exicon) carries a line of TO-3 devices and one of the above URLs has a crosswalk table to match the original Hitachi device numbers to theirs. Rumor has it that when Hitachi no longer supplied the lateral MOSFETs others, such as EXICON, began to supply the market.

I don't know for sure what you have but I think it is an EXICON product with the device number on it as specified by Hafler.

Remember, you can't just replace one MOSFET in a matched pair or trio. All devices used in parallel must be matched on Vgs and matched pairs or triplets get expensive. Early on in MOSFET history designers claimed these devices could easily be paralleled to provide greater output. Then, they started to say that this was possible IF the devices had the same date or batch code. Then, they began to realize that paralleling might be OK if resistors (.1 ohm, for example) were placed between the source and outputs. What you need is a matched triplet for N-channel and a matched triplet for P-channel devices.

A missing MOSFET or two in a DH-500 is a bummer. You will have a problem getting a matched replacement. What are the Hafler grade numbers of your other MOSFETs?

"Bear" who posts here may be able to help. He is in the business. You'll have to look him up at the registered user list. SoundValves may help but they may not have the grade number device/s you need and they won't be cheap.
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Old 25th March 2005, 02:30 PM   #3
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Hi Dick,


Thanks for the response. I was able to D/L the DH500 manual and I see that the QN113 and QP113 are Hafler part numbers and they represent 2SK176 and 2SJ56. The ones I am missing are the 2SK176. All three are from the same heatsink.

So, my question is that when you say they must be matched, are you saying that these three need to match each other or do they also need to match the three 2SJ56 as well? Can I just install three matched 2SK176?

The P500 has quite a bit more circuitry than the DH500. It has a Volume control circuit and is set up to run in strapped mode. It also has balanced inputs. It's missing the bridge so I haven't been able to check anything else yet. I isolated the secondary leads and gave the amp power using the light bulb trick and the fan on the heatsink runs, so at least that part is working.

Thanks again, Terry
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Old 25th March 2005, 03:36 PM   #4
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Which version of circuit cards do you have? Do they look like the DH-220 cards such as in your P-225 (P-230)? If so, you can use the bridging wiring diagram for the DH-220 bridging kit and these instructions are at the end of the DH-220 manual available from Hafler. The P500 should bridge in the same manner.

The balanced input schematic should be quite standard and similar to that used in other P versions. Do these balanced inputs go to their own separate smaller circuit board? You could examine the schematic for the Hafler P-1200 to get an idea of what to look for to handle balanced inputs. Can you supply a picture of the inside of the amp?

MOSFETs when used in parallel, in dual or triplet, must be matched to each other. The P channel paralleled devices must be matched to each other in that channel. Ditto for the N-channel devices. The P device sets in a channel do NOT need to be matched to the N device sets in that channel.

All your MOSFETs should have a Hafler grade number (1 through 7) stenciled to the top of their cases -- I guess. The older amps did. However I have a set of 12 MOSFETs here that came from a DH-500 and all have the same part numbers as yours but they are NOT marked with a grade number -- but -- they all are matched triplets based on readings from my Hafler MOSFET checker and have their grade number written on them. Hafler may have been able to get pre-matched sets from their supplier. Confusing? I'll send a picture in my next response.

As I told you in my email, for trouble shooting purposes, you can run this amp with fewer than 6 MOSFETs per channel. You could set one channel to run from 4 MOSFETs and take the extra MOSFETs and install them in the other channel. This other channel then could be run with only one N and P device. This assumes you will re-bias each channel as needed to adjust to the use of a smaller number of MOSFETs -- and that you will not be running up the channels at a high wattage level.

The fan runs from 120 VAC so its performance is a no-brainer.

Hope this helps.......
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Old 25th March 2005, 04:45 PM   #5
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MOSFET matching importance depends on Rds-on with lower values requiring thighter matching. Lateral MOSFETs with Rds-on in the range of 1 ohm require very little matching efforts while vertical MOSFETs with Rds-on in the range of 0.05 ohms require not only careful matching but additional source resistors
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Old 25th March 2005, 04:52 PM   #6
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eVA,

Good info about differences between lateral and vertical MOSFETs. Can you explain to Terry (and me) how to measure Rds of lateral MOSETs and what range is to be expected for those devices as used in a DH-600?

Note, this amp does not use source resistors.

Here is a picture of my set from a DH-500 and they all matched correctly as measured on my Hafler MOSFET checker.
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File Type: jpg dh-500mosfets.jpg (48.6 KB, 322 views)
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Old 25th March 2005, 04:53 PM   #7
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Terry,

Does your P-600 have a board similar to this one? It is the balanced input and level control board from a P-1200.
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File Type: jpg balancedinput.jpg (50.9 KB, 320 views)
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Old 25th March 2005, 06:14 PM   #8
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Hi guys,

Thanks for the kind help.

OK, it's good to know that I would only have to replace the three missing MOSFETs and not all 6. Of course that's assuming that the ones that are here are OK. Profusion wants over $12 each for them and I'm not sure if they are matched.

I will have to check things when I get home to see what style of boards I have. I didn't know what to look for prior to your posts.

The MOSFETs that are in my P500 do have that number stamped on the case. I think the ones that are visible have a 9 or a 6 on them.

That board does look familiar. I will check when I get home. There are 4 boards in this amp if memory serves me correctly. The two mounted on the heatsinks and then one in the front for the gain knobs and one in the rear for the balanced circuit, I think.

I will take some pics of the insides too. This is much more cluttered than the DH500 from what I can tell.

Blessings, Terry
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Old 25th March 2005, 06:31 PM   #9
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Actually Rds-on is not useful for matching, Vgs-on threshold and transconductance are the parameters that matter

In practice :

For each device you may try finding the required Vgs to obtain certain Id values while keeping Vds constant and high enough [24V], let's say Id=500mA and Id=2.5A. Then just place together the devices with closer values of Vgs for both current levels

Vertical MOSFETs have not only lower Rds-on but higher transconductance, so any threshold or transconductance mismatch translates into a much higher Id mismatch
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Old 25th March 2005, 07:04 PM   #10
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Terry,

The number stamped on the MOSFETs you see is probably a 6. The Hafler grading numbers only went from 1 through 7. SoundValves 3-4 years ago sold DH-500 kits (until all its extra parts were used up). They used EXICON mosfets. I bought some from SoundValves at that time and they all were grade 6. So, you might get lucky with a purchase of some from exicon and you might not. Exicon does not sell matched sets as far as I know. SoundValves bought several hundred of them, measured each one, and then put them into matched sets. You might have to purchase 10 or 15 of them to get a set of 3 that match.

I have a set of DH-500 mosfets here (as in the picture above) and these triplets have these grade numbers:

6 of QN -- grade 2
3 of QP -- grade 3
3 of QP -- grade 5

As Eva pointed out (as did I earlier) you might get by with the use of source resistors. Some amps use these, usually a .1 ohm 5 watt non-inductive resistor. But, then, you would have to use such a resistor on all 12 mosfets to keep channel balances.

Eva talks about vertical MOSFETs but your amp uses lateral mosfets. There are several parameters to measure for a mosfet but the primary matching is for Vgs, which is what Hafler did and is what the grade numbers stamped on your devices represent.

Terry, I will send you an email about this.
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