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Finding replacement transistors for early Marantz

saabracer23

saabracer23

AK Subscriber
Subscriber
I was curious if there was anyone that has come up with a way to cross reference replacements for older marantz 34-**** transistors. I have a tone board with 34-1008, 34-1010, and 34-1031 that is making some noise and I can’t seem to find any input on good replacements.

Dan
 
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Hello Dan

Giving a "cross list" is not the good way to act
Because Marantz transistors are selected by specifications for the factory .
Today nobody know what these specifications are and last time I saw SID SMITH I did not have enought time to ask him all the questions I wish to ask .
Making a cross list again is not good . For example If we know what a 34-1010 is a xxxxxxx ( commercial type ) we will never be able to make the same sort as those made by the factory because we don't know them !
To resolve your problem , the most important thing is to know what kind of noise you are talking about .
Then the problem may not come from your transistors I know it is not easy but can't you try to make substitution between left and right channel to confirm that this "noise" is coming from a transistor or not ?
 
clinic-audio said:
Hello Dan

Giving a "cross list" is not the good way to act
Because Marantz transistors are selected by specifications for the factory .
Today nobody know what these specifications are and last time I saw SID SMITH I did not have enought time to ask him all the questions I wish to ask .
Making a cross list again is not good . For example If we know what a 34-1010 is a xxxxxxx ( commercial type ) we will never be able to make the same sort as those made by the factory because we don't know them !
To resolve your problem , the most important thing is to know what kind of noise you are talking about .
Then the problem may not come from your transistors I know it is not easy but can't you try to make substitution between left and right channel to confirm that this "noise" is coming from a transistor or not ?
Click to expand...

Thank you for the reply. Through swapping input and output cables on the boards I have the issue narrowed down to the tone board on channel B. it makes a periodic clicking or static noise, not constant, it’ll come and go at. The only problem is that I have no idea how to take the tone board out. The pots are mounted to the front normally, but the back is held by an adhesive strip that will not let go and I don’t want to damage the board by prying. Unfortunately there isn’t enough room to get a blade under it to cut the adhesive strip.
F377FAE7-C7FB-4C4A-AD46-41DDE20DE315.jpeg


The reason I believe it’s transistors is because the moment I freeze spray Q1003 and Q1004 (34-1008 and 34-1031) the noise goes away completely until the transistors have had a chance to warm up again.

81FC4A4A-57AB-4866-864C-B985367F7E51.jpeg

To replace the electrolytics I had to cut the old ones out leaving a lead coming through the board and I soldered the new cap leads to the old one sticking out. I’m afraid I’ll have to do the same with these transistors, I just need to know what will work there.

2BFBA8EF-777F-494D-977D-F45D0C60774F.jpeg

Dan
 
Interestingly enough, when I freeze sprayed those two transistors to take the pic the noise went away as it had every other time, but it’s been about an hour and the noise hasn’t returned....

I know the issue is in one of those transistors so I’d like to replace them since there is obviously an issue. What would I do if they were to completely fail, I’d have to put something in.

Dan
 
John at Instrument Resources had figured out working substitutes for many Marantz branded parts. I have not been able to reach him for quite a while, I hope he is OK.
My new and 1985 NTE cross references list a few 34-XXXX substitutes for whatever that is worth.
My ECG cross reference from 1978 contains similar info. Maybe you could use this info as a clue.
YMMV
This is the primary reason I don't work on the older Marantz models.

Tom
 
saabracer23 said:
I was curious if there was anyone that has come up with a way to cross reference replacements for older Marantz 34-**** transistors. I have a tone board with 34-1008, 34-1010, and 34-1031 that is making some noise and I can’t seem to find any input on good replacements.


Check this thread out as for as a cross reference. The author appears to have put some time into creating it.

https://audiokarma.org/forums/index.php?threads/marantz-19.903790/


Regarding board removal. You are correct. After removing the front pot nuts, the only thing holding it in is adhesive. I was able to remove the tone board in my Model 19 by taking my time and just starting in one corner. I was sure something else was holding the tone board down because the adhesive was fairly strong. However, it did pull up. Once you get it going, just move slow across the back of the board. Much easier to work on when removed.
Click to expand...
 
catrafter said:
John at Instrument Resources had figured out working substitutes for many Marantz branded parts. I have not been able to reach him for quite a while, I hope he is OK.
My new and 1985 NTE cross references list a few 34-XXXX substitutes for whatever that is worth.
My ECG cross reference from 1978 contains similar info. Maybe you could use this info as a clue.
YMMV
This is the primary reason I don't work on the older Marantz models.

Tom
Click to expand...
Yes. There is not nearly the information available on the older units.......which leads to problems.
 
I would measure the voltages on the transistors to get an idea of what the Vceo needs to be, then cut the leads on the noisy ones, and put them in my "El-lCheapo Chinese" component tester to see the polarity, pinout, and measure the HFE (with it cold), then pick something appropriate. I would bet a cup of coffee that a 2SC1815(GR) would replace an npn, and 2SA1015(GR) would replace a PNP. Both are low noise audio transistors with a Vcbo of 60 v, Vceo of 50 v, Ic of 150 ma, and an HFE of 200-400. There are other HFE values available (they have different suffix letters)
 
Jamie Starr said:
Check this thread out as for as a cross reference. The author appears to have put some time into creating it.

https://audiokarma.org/forums/index.php?threads/marantz-19.903790/


Regarding board removal. You are correct. After removing the front pot nuts, the only thing holding it in is adhesive. I was able to remove the tone board in my Model 19 by taking my time and just starting in one corner. I was sure something else was holding the tone board down because the adhesive was fairly strong. However, it did pull up. Once you get it going, just move slow across the back of the board. Much easier to work on when removed.
Click to expand...

Thanks for the suggestion, unfortunately it doesn’t help me with the 34-1008 or 34-1031 and those are the only two needed. For the 34-1008 there is only a single NTE component listed and I'm not a huge fan nor do I trust NTE. Nothing listed at all for the 34-1031.

AE Bob said:
I would measure the voltages on the transistors to get an idea of what the Vceo needs to be, then cut the leads on the noisy ones, and put them in my "El-lCheapo Chinese" component tester to see the polarity, pinout, and measure the HFE (with it cold), then pick something appropriate. I would bet a cup of coffee that a 2SC1815(GR) would replace an npn, and 2SA1015(GR) would replace a PNP. Both are low noise audio transistors with a Vcbo of 60 v, Vceo of 50 v, Ic of 150 ma, and an HFE of 200-400. There are other HFE values available (they have different suffix letters)
Click to expand...

Thank you for the suggestion, I appreciate it and it may be the best option. I powered the receiver down and left it off for about an hour. Powered it back up and it’s been on for another hour or so and it hasn’t made a peep, both channels are dead silent and sound great. Not sure why freezing those two transistors that last time would “fix” it, but I’m tempted to leave it if there doesn’t seem to be a known go to for replacement. It just seems like on of these might be on the way out and figure it’d be best to take care of it now instead of 2 months down the road.

Dan
 
AE Bob said:
I would measure the voltages on the transistors to get an idea of what the Vceo needs to be, then cut the leads on the noisy ones, and put them in my "El-lCheapo Chinese" component tester to see the polarity, pinout, and measure the HFE (with it cold), then pick something appropriate. I would bet a cup of coffee that a 2SC1815(GR) would replace an npn, and 2SA1015(GR) would replace a PNP. Both are low noise audio transistors with a Vcbo of 60 v, Vceo of 50 v, Ic of 150 ma, and an HFE of 200-400. There are other HFE values available (they have different suffix letters)
Click to expand...


Measuring to ground on 34-1008 I’ve got
E: .708V
B: .16V
C: -36.3V


On 34-1031
E: -36.8V
B: -36.4V
C: -20.9V

So for the 34-1008 I’d want something with a Vceo of more than 37V? And 57V for 34-1031?


Dan
 
Apparently the 34-1008 is a PNP and as you said has 37 volts between E&C. The 34-1013 is apparently an NPN but it only has 16 volts between E&C. You can look at the actual B+ (B-) feeding the circuit to determine the maximum voltage the transistor could ever see, and choose devices that have a higher breakdown voltage. I think if you have high enough breakdown voltage, close enough gain, and low noise devices, they will work fine for you. Those preamp transistors likely have very low current flow (you can determine the maximum by analyzing the circuit). What model Marantz is it?
 
AE Bob said:
Apparently the 34-1008 is a PNP and as you said has 37 volts between E&C. The 34-1013 is apparently an NPN but it only has 16 volts between E&C. You can look at the actual B+ (B-) feeding the circuit to determine the maximum voltage the transistor could ever see, and choose devices that have a higher breakdown voltage. I think if you have high enough breakdown voltage, close enough gain, and low noise devices, they will work fine for you. Those preamp transistors likely have very low current flow (you can determine the maximum by analyzing the circuit). What model Marantz is it?
Click to expand...

Thank you, I appreciate the assistance! It’s a model Nineteen. Here is the tone board circuit, I’m dealing with Q1003 which is a 34-1008 and Q1004, a 34-1031. I took a screen shot of the schematic as a whole and then zoomed in as AK tends to compress the images making them hard to read.

Dan

08626F1E-5AC5-4885-840B-1E182245C6CB.png DE787A21-31D2-4546-8213-8EA9239C5077.png 42B1A3AE-F563-45F3-8D77-66288E64665C.png
 
Well it looks like the maximum voltage that could ever appear across the transistor is 48 volts (-36 to +12). The maximum current would be very low due to the large resistors in the circuit. If it were me I would try 2SC1815GR (KSC1815GR) and 2SA1015GR (KSA1015GR) in the noisy channel, and see if there is any audible difference with the other channel. If they sound the same, I would change the devices in the other channel also.

The voltages on the schematic look a little strange for silicon transistors. I would expect there to be about 0.6 volts between emitter and base, but in the schematic it shows 0.5 for one, and 0.44 for the other. It might be due to the high impedance of the circuit, and the loading of the meter the voltages were taken with??????
 
Last edited:
AE Bob said:
Well it looks like the maximum voltage that could ever appear across the transistor is 48 volts (-36 to +12). The maximum current would be very low due to the large resistors in the circuit. If it were me I would try 2SC1815GR (KSC1815GR) and 2SA1015GR (KSA1015GR) in the noisy channel, and see if there is any audible difference with the other channel. If they sound the same, I would change the devices in the other channel also.

The voltages on the schematic look a little strange for silicon transistors. I would expect there to be about 0.6 volts between emitter and base, but in the schematic it shows 0.5 for one, and 0.44 for the other. It might be due to the high impedance of the circuit, and the loading of the meter the voltages were taken with??????
Click to expand...

Looking through my stash and I have the KSA1015YTA, but not the KSC1815YTA (will the YTA be okay in place of the GR?).

I was looking to see what I had to put in place of the 1815

I have the KSC1845 (lower Ic at .05). Do you think the current demand will be low enough?

I have the 2N3904 and BC550B, but maybe the Vce will be too low? Vce of 40V for the 2N3904 and 45V for the BC550B. Might still be okay with the voltages I measured.

Lastly I have the ZTX696B, which is way overkill in it’s ratings, but I’m wondering if the gain is too high. It’s rated with an hFE of 500 min, the ones I have are measuring at about 800 on my Peak Atlas DCA75.

Truthfully though the 34-1008 (PNP) is the device with the actual issue. Since I have the KSA1015YTA I’m wondering if I should just replace the bad device and leave the other one as is. Or should I replace them as a pair?

Do any other other NPNs I list look like they might work? Oh and the noise returned, boooo.

Thank you again,
Dan.
 
If the PNP is the only one that is noisy, I would try just replacing it first (with the KSA1015).

In my experience the actual gain of transistors is not as critical as some make it out to be. The design of most circuits have enough negative feedback to swamp out the majority of the gain of the device anyway.
 
AE Bob said:
If the PNP is the only one that is noisy, I would try just replacing it first (with the KSA1015).

In my experience the actual gain of transistors is not as critical as some make it out to be. The design of most circuits have enough negative feedback to swamp out the majority of the gain of the device anyway.
Click to expand...

Sweet, thanks!

Dan
 
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