SDT-04 thermistor replacement needed.... (2024)

G

Gordy

Active Member
  • Apr 15, 2015
  • #1

This is for a Marantz 2220B. I ordered an identical replacement on the web and it's now over a month, and so far it's not here. I called the source and was told they didn't have any, bet they would send when they did.....Is there a suitable replacement I can JB weld to a heat sink mount? I've JB welded a thermistor just this way on an Accuphase P-300 amp, (thanks Echowars), and it worked perfectly. Thanks.

http://products.pacparts.com/jvc_sdt04_n_thermistor_1102893097.php

Last edited:

sKiZo

Hates received: 92644 43.20°N 85.50°W
  • Apr 15, 2015
  • #2

I suppose a CL80 or CL90 is out of the question?

PS ... I like the idea of the JB Weld and heatsink ... gonna have to try that someday.

avionic

" Black Knights "------- F-15 " Wizard "

Subscriber

  • Apr 15, 2015
  • #3

sKiZo said:

I suppose a CL80 or CL90 is out of the question?

PS ... I like the idea of the JB Weld and heatsink ... gonna have to try that someday.

Not even close.

JURB

Super Member
  • Apr 15, 2015
  • #4

Take them both out and jump them out. DO NOT READJUST THE BIAS !

Then you need a pot of cold water, an accurate thermometer and an ohmmeter. Derive the coefficient by heating up the water and measuring the resistance at about six or seven temperatures between about cold water and up to about steamng water. Might as well take the readings in centigrade because that's what they use.

With the specs you can go to the selector pages at Mouser, Digikey, Newark or others and find a replacement.

If you do not adjust the bias you can run the unit until a replacement is procured. It will have slightly more distortion at very low listening levels. You may or may not hear it actually, these are not a whole bias network here, not by any stretch. you could jump the one out and find out if you cna hear a difference but we need the good one to measure. Unless you want to get into it twice.

Of course if the thermister is fried so is the 82 ohm across it.

If you can't find the same resistance and coefficient, the wicket gets sticky. We'll burn that bridge when we come to it.

G

Gordy

Active Member
  • Apr 15, 2015
  • #5

JURB, interesting....I'll do it and report back. I'm not sure if they're shot or not. One broke it's lead right up close to it's body and would be just about impossible to re-solder. The receiver wasn't working to begin with, it had a break on the board which broke a couple of traces. I glued the board and jumped the traces. Also replaced main PS caps, originals were shot.

JURB

Super Member
  • Apr 15, 2015
  • #6

In that case just temporarily jump it out and get it working first. But just don't set the bias.

One thing at a time.

On the one that is good you might want to put a little glue right where the leads go in. I couldn't find a spec sheet on it so we need that to determine what can go in there.

G

Gordy

Active Member
  • Apr 19, 2015
  • #7

finally got back to testing thermistor..

I managed to break the lead on the other one taking it off.... I also managed to scrape away enough to get a good solder connection. There is a yellow dot on one side, does this indicate a polarity? One of these thermistors measures both ways, the other only one way. It stayed polarized even after heating it to 200+ F. Anyway here are the results from heating in water, meat thermometer measuring temp in F. I'll convert to C in the next post.
Room temp 70.......... .89 meg ohm
100F....................... .82 meg ohm
110F....................... .75 meg ohm
120F........................ .70 meg ohm
130F........................ .67 meg ohm
140F........................ .63 meg ohm
150F......................... .58 meg ohm
160F........................ .51 meg ohm
170F........................ .507 meg ohm
180F........................ 500K ohm
190F........................ 470K ohm
200F........................ 430K ohm

After it cooled down it went back to.89 meg ohm.

EchoWars

Hiding in Honduras

Sponsor

  • Apr 20, 2015
  • #8

So, at room temp, effective resistance for setting up the bias current is:
82Ω||890K = 81.992Ω

At 200°F, we get:
82Ω||430K = 81.984Ω

See the problem here?

The resistance of that sucker ought to be a few KΩ at room temp, at the most.

Your method, your meter, or your device needs some scrutiny here.

G

Gordy

Active Member
  • Apr 20, 2015
  • #9

Meter should be good, I double checked with another meter. Method...dunno, but should be OK. The devices are suspect, though. The other thermistor( not the one I measured in the above post) checked out at 420k ohm at room temp and tapered down to 21k ohm at 212 deg. F. I also got a measurement from it if I reversed the leads. With the thermistor measured in the above post, I only got a reading with the neg meter lead on the side of the thermistor with the yellow dot on it. Not sure what all this means? Maybe they're both screwed. To bad... I was hoping I could add some useful info to the forum.

Last edited:

Tom B

AK Subscriber

Subscriber

  • Apr 20, 2015
  • #10

These devices are really like multiple diodes in series. They should read close to infinity in the reverse direction, and as a 3, or 4 diode in series device in the forward direction. Looking at the manuals and schematics, they show a part number of STU-3H, or SV-3A, depending on whether you look at the 2220, or 2220B. My concern is that you are looking for SDT-04, which I believe is a 4 diode junctions in series device. The manual specifies 3H or 3A which are equiv of 3 diode junctions in series. The "4's would have a lot higher DC resistance than the "3"'s . "3"s are the most common I have seen in receivers, but have seen "2"s, and "4"s. Could someone have worked on your unit previous, and put "4"s in there???
I have a number of used Driver boards with bias diodes, I may be able to help you out with, but need to know what the originals were, or should be.

Tom B

AK Subscriber

Subscriber

  • Apr 20, 2015
  • #11

I misread this request of yours. For whatever reason, I thought you were talking about the bias diode mounted to the heat sink, when you referenced the jbweld. Some refer to these bias diodes as varistors, and thermistors.
I now look at the schematic again and see the thermistor you are referring to. (SDT-04). I don't do a lot of work on Marantz's so I don't thin I have any of these. I mostly work on Pioneers, who don't use many thermistors. But I will look anyway

dshoaf

That high voltage buzz
  • Apr 20, 2015
  • #12

Where, exactly, are these devices being used in the 2220 receiver? A schematic and location would be helpful to to understand the application in the receiver.

I don't recall thermistors being used in this receiver. Is this being used in-line with the primary or secondary side of the power transformer?

Cheers,

David

G

Gordy

Active Member
  • Apr 20, 2015
  • #13

Well I guess this proves a little knowledge can be a dangerous thing. The part I'm talking about IS a diode...STU-3H. Not STD-04. These two STU-3H are mounted to the heat sink and wired to J706/708 and J705/707 of the power board. I'm sorry for the confusion, I thought they were thermistors (being they are mounted on the heat sink) The STD-04s are thermistors.The STD-04s are sandwiched between H721/723 and H722/724 and wrapped in shrink tubing. So I guess what I need is a replacement for an STU-3H. The only marking on the STU-3H is the number 55 and a yellow dot on one side.

Last edited:

EchoWars

Hiding in Honduras

Sponsor

  • Apr 20, 2015
  • #14

Here:

Attachments

  • 2220B_Amp_Scat.jpg

    116.7 KB· Views: 59

avionic

" Black Knights "------- F-15 " Wizard "

Subscriber

  • Apr 20, 2015
  • #16

gordy said:

well i guess this proves a little knowledge can be a dangerous thing. The part i'm talking about is a diode...stu-3h. Not std-04. These two stu-3h are mounted to the heat sink and wired to j706/708 and j705/707 of the power board. I'm sorry for the confusion, i thought they were thermistors (being they are mounted on the heat sink) the std-04s are thermistors.the std-04s are sandwiched between h721/723 and h722/724 and wrapped in shrink tubing. So i guess what i need is a replacement for an stu-3h. The only marking on the stu-3h is the number 55 and a yellow dot on one side.

stv-3h

EchoWars

Hiding in Honduras

Sponsor

  • Apr 22, 2015
  • #17

EchoWars said:

Your method, your meter, or your device needs some scrutiny here.

So, method it is. With a device misidentification thrown in for flavor.

The yellow dot denotes the cathode (IIRC).

I do not know of a source for new parts.

Auction:
#131477702190
380416094305

The seller in Germany has a bunch of unused ones (NOS). That's the route I'd likely go.

Edit: I'm assuming that you are looking to replace the STV-style (the 'horseshoe' shaped one with radial leads). The axial device is an SV-03, such as auction #140911974352.

Last edited:

You must log in or register to reply here.

SDT-04 thermistor replacement needed.... (2024)

References

Top Articles
Latest Posts
Article information

Author: Nathanael Baumbach

Last Updated:

Views: 5938

Rating: 4.4 / 5 (75 voted)

Reviews: 90% of readers found this page helpful

Author information

Name: Nathanael Baumbach

Birthday: 1998-12-02

Address: Apt. 829 751 Glover View, West Orlando, IN 22436

Phone: +901025288581

Job: Internal IT Coordinator

Hobby: Gunsmithing, Motor sports, Flying, Skiing, Hooping, Lego building, Ice skating

Introduction: My name is Nathanael Baumbach, I am a fantastic, nice, victorious, brave, healthy, cute, glorious person who loves writing and wants to share my knowledge and understanding with you.