• Please note that Audiokarma will be offline briefly for updates early on Monday morning, September 28th.

Marantz 1150 finally fixed

Richs_Trains

Richs_Trains

Well-Known Member
Hey all, Got some help on my 1150 but I posted in barter town and that was the wrong place. I am going to order the suggested transistors for the differential pairs, but figured I may as well replace the other transistors on the power amps while I am at it (the static problem sure sounds like a transistor, but it never lasts long enough for me to hit it with freeze spray and it is so intermittent it's driving me nuts). I can never find the original part numbers on Mouser, but every time I ask on here people know the current replacement. Where can I cross-reference old part numbers to current offerings so I don't have to keep bothering everyone here? I am looking for:

2SA721
2SC945
2SA733
2SC496
2SA794
2SC1567
2SC1625
2SA815

Thank you to everyone that helped me in the barter town post and for any help on this post.

Rich
 
Last edited:
Register to hide this ad
avionic said:
KSA733C -- https://www.digikey.com/product-detail/en/on-semiconductor/KSA733CYTA/KSA733CYTACT-ND/4314803
KSC945C -- https://www.digikey.com/product-detail/en/on-semiconductor/KSC945CYTA/KSC945CYTACT-ND/4553043
Click to expand...
Thank you avionic, hoping to get everything from Mouser to save on shipping and they don't seem to have these, but will go to Digikey is necessary. I have the right power amp pulled right now and it seems to be running fine (only time will tell as this problem is very intermittent) and whoever worked on the amp before wrote notes on the right channel PCB (I got this in pieces and missing one board, all the knobs, bottom cover, feet, and a selector switch, but would like to make it whole) Thanks again Rich
 
I would try using 'freeze spray' and/or a low temp heat gun (not the paint stripper one) to see if I could make it act up, or quit acting up once it starts.
A hair dryer can be used as a low temp heat gun.
Replacing the differential pair (H701 and H702) with Hfe matched KSC1845's bonded together with heat shrink (and a tiny smear of thermal compound) may solve the problem.
There are only three electrolytic capacitors, so I would replace those just to be sure.
H715 and/or H716 are also suspect, they are 15V zener diodes, 500mW should be fine.
I would not wholesale swap other semiconductors. If you determine that one is bad, then change it.
BTW, on the 1150 amp, the input 'ground' is separate from the output 'ground', so both plugs on an amp module have to be installed or that amp module won't work properly.
I've not worked on an 1150, so all this is based on my experience with other gear and the 1150D schematic.

YMMV
Tom
 
catrafter said:
Replacing the differential pair (H701 and H702) with Hfe matched KSC1845's bonded together with heat shrink (and a tiny smear of thermal compound) may solve the problem.
Click to expand...
Thanks Tom, This was the only spot I got a variance when I hit it with freeze spray and was going to for sure change these, just tired of thinking it was fixed only to have it fail again when put back in the listening rotation. I have a shopping cart at Mouser with the KSC1845's in it (100) and figure I can at least get two matched from there (50 was more expensive than 100). I will definitely replace the electrolytic caps and check the diodes you mentioned. I am pretty sure the 1150 and 1150d use the same power amp sections. Right now the right amp is removed and the unit seems to be working fine. When I bond the KSC1845's (flat side to flat side) will they go in pin for pin as the ones removed? And, since I will have 98 extra KSC1845's are these used often in Marantz amps? Thanks for your help, Tom. Rich
 
The KSC1845 (F gain code) should go in exactly like the old ones...match the silk screen on the board.
These transistors can be used as differential pairs in your 1150D and most any Marantz with NPN differential pairs as long as the original parts are Japanese style 2SCXXX parts.
If you need PNP differential amp pairs for amps that use 2SAXXX then KSA992(F gain code) should work fine, match them for hfe as well.

Tom
 
catrafter said:
Replacing the differential pair (H701 and H702) with Hfe matched KSC1845's bonded together with heat shrink (and a tiny smear of thermal compound) may solve the problem.
There are only three electrolytic capacitors, so I would replace those just to be sure.
H715 and/or H716 are also suspect, they are 15V zener diodes, 500mW should be fine.
Click to expand...

Tom, I replaced the differential pair, the three caps, and the two diodes you recommended and the problem remains, so I decided to switch the amplifier boards (changing the brackets on both, should have done this first) and the problem stays with the right channel. So, I guess I was wrong about it being in the amp board. I have a low rumble and slight static in the right channel that becomes loud static intermittently and it does not change with the volume control or with the tone selector set to in or out. Also, sliding the balance control has no effect on the noise. I have re-capped the power supply board and the vertical board behind the tone controls in the past trying to nail down this problem. I again tried freeze spray and was able to induce the heavy static when I hit the board that the tone selector switches are on (tone volume board) and although hard to see when the unit is assembled it appeared to be HH04 or HH02 listed as a 2SA836D or E and a 2SC1345D or E. Does this sound like it could be my problem and if so, is there a cross for these two transistors I can use. Thanks again, Rich
 
Hi Rich,
If those transistors are sensitive to thermal shock, I would probably use KSA992F for the 2SA836D and KSC1845F for the 2SC1345D. The Ft for the replacements is lower than the originals, but I don't think that would be an issue.

Let us know how it turns out.

Tom
 
catrafter said:
Let us know how it turns out.
Click to expand...

Tom, I replaced the transistors with the ones you suggested (lucky I consulted the datasheet on the new ones, as I was about to put them in backward!). Powered it up and no background noise on the right channel! Connected a source, and it is playing right now. Only time will tell if I actually fixed the problem, but I have high hopes this was it. Thank you so much, have been wrestling with this for a while now. Going to let it play a bit and then adjust the amps and hopefully, it is fixed. Thanks again! Rich
 
Richs_Trains said:
but will go to Digikey is necessary.
Click to expand...

If you do roll over to digikey and want to, you can take advantage of their free shipping US and Canada. Send em a check with tax (if required) and bam they send you your order.

I get orders from Digikey using snail mail to them in about the same amount of time I get orders from Mouser using the less expensive shipping alternatives. The Priority Mail from Digikey gets here so much quicker than that crappy UPS mail innovations where Mouser puts it on a truck from UPS going to who knows where and then it lands at a Post Office for further processing before finally making it to may part of the world and eventually my mailbox.
 
You must log in or register to reply here.
Back
Top Bottom