Marantz 1030 Problem(s)

[Nac458]

Hello all,

So there I was.

I had just completed an entire re-cap for the little 1030 amp. I was excited to hit the switch and resolve the "bad capacitor problem" on the power amp board. But upon doing so, only the left channel was able to come through and I was left disheartened and discouraged.

Upon further inspection I replaced a few fried resistors that slipped my eye but alas, still nothing from the right channel. So I took some time to watch this video:

(and I learned quite a few things).

As I'm a hobbyist, I don't have much test equipment, nor do I have experience with such. So I decided to replace the transistors on the pre-amp board and most on the power amp board in hope of bringing the right channel back and giving it a clean bill of health. Note that I now receive no sound from either channel, and the resistor R738 is smoking and burning up after the transistor swap, while the other R737 sits content.

Unfortunately, I did not do my homework before diving in, and I'm left stuck with the following NTE (yeah, I know ) replacements on the boards (currently):

POWER AMP BOARD

H709-H712: (2SC959, 2SA606) with NTE128 - I know these NTE parts are all NPN transistors and they should be NPN/PNP pairs, respectively. I will have appropriate PNP transistors for H711 & H712.

H705-H706: (2SC371) with NTE 289A

H707-H708: (2SA562) with NTE 290A

PRE AMP BOARD

H501-H506: (2SC458) with NTE 85

Is this a transistor problem, or does the problem lie somewhere in the bias?

Any help would be most appreciated.
Thanks!

 

[Bert 1100]

Sorry to hear about your troubles....
Did both channels work before you did the recap?
If yes, I would re-install all the old transistors in there. Then carefully check for proper polarity on the new caps. Also check for broken wires from moving the boards around.
Probably only the 2sc485 need replacing, they are know to become noisy with age. They can be replaced with KSC1845. About the other transistors somebody more knowledgable might advise better.
Good luck.

 

[Nac458]

Bert,

Thanks for the info. I recently learned that NTE isn't too highly regarded in the hi-fi repair world.

No - only the left channel worked. I went ahead and replaced all components as they have seen 30+ years of use (or abuse).

But regardless, I'll take your advice and look into the other replacement transistor.
I'm going to begin by getting the correct NPN/PNP transistor pair that I mentioned before at H709-H712.

 

[catrafter]

This is what I would use:
Phono Preamp:
H901, H902, H903 H904 = KSC1845

Tone/preamp:
H501, H502, H503, H504 = KSC1845

Power amp:
H701, H702 = KSC945C
H705, H706 = KSC1845
H707, H708 = KSA992
H703, H704, H709, H710 = 2N3440 ST Micro brand if possible
H711, H712 = 2N5416 ST Micro brand if possible

H708, H710, H711, H712 will require press on heat sinks such as Aavid Thermalloy 323005B00000G
You can remove H705, H706, H707, H708 while testing, they limit the output when driving reactive loads, put them in after you have it working.

Tom

 

[Nac458]

Tom,

Thanks for your recommendations!

I'll go ahead and order the respective transistors with my next part order.

Also, would it be wise to replace the trimming resistors (R723,R724,R729,R730) at the top along with the varistors (H713,H714)? I'm having trouble finding a comparable varistors, and diodes, for that matter.

- Nicholas

 

[catrafter]

I normally just clean the trimmers. I don't recall what the so called 'varistors' are in the 1030, if they are the green or red 'gob' diodes, then measure one with the diode function on a DMM to see what the forward voltage drop is, then series enough 1N4448 diodes to get that voltage. The 'gob' diodes don't have a very good track record, I always replace them.

Tom

 

[tonebells]

I have H713,H714 as one 1N4148 for each.

 

[Nac458]

So far, no luck.

This is definitely a learning process. Lots of work, but almost twice the amount of learning.

(On a side note, I've brought a 2270 back to life! Man, that thing sounds incredible.)

I'm going to proceed to remove (and possibly replace) the output transistors on this little 1030.

They're the only thing I can imagine that would be causing the power amp board any harm.

 

[KutzlerTrans]

Remember to fix one board at a time and test afterwards with a dim bulb tester. just cobble a lamp in series. that (may) will help you from smoking it. 50w bulb would be a starting point. I am not sure.
The most important thing about substitute transistors is the EBC layout. they may be different, even though its the same inside. smoking resistors is definitely a result of wrong pin outs. Toms advice is Spot On!
I read on another thread that the
pin-order for the original 2SC458 is "BCE" whereas that for the KSC1845 is the common standard "ECB.
Stolen info from http://www.audiokarma.org/forums/in...oration-and-upgrade-of-a-marantz-2325.689386/
Post# 12
Just make sure to check before installing.
John

 

[Nac458]

John,

That is definitely something I overlooked in my process of replacing the components on the amp board.
Shoulda been more careful

I'll go back and thoroughly inspect those transistors.

- Nicholas

 

[KutzlerTrans]

Check this out! http://www.ebay.com/itm/like/181861306612?ul_noapp=true&chn=ps&lpid=82

These things are fantastic.