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Please help my problem on Marantz 1180

lwong2's picture

I hereby wishing all Hifi engine friends A Happy and Prosperous New Year 2014
I got a problem which needs an expert advice

The Peak light of my Marantz 1180 DC amplifier was lighted up. Upon checking i found a capacitor ( 100 uf 16 V) item C 856 was bulged up. I replaced it with a Sanyo Oscon cap 100 uf 20V. After playing the amp for awhile the same problem surfaced.

I hope some one can advice me what has gone wrong and what i should do to put back to normal. I am a novice in electronic

Thank you



Please help my problem on Marantz 1180

Hello,

I can't find a schematic for the 1180dc, but did find the 1152dc which appears very similar. If the new cap C856 has also expanded after replacement, you probably have an issue with high DC voltage across this cap causing a problem (or the new one was installed backwards) verify that the polarity of the capacitor is correct (+ marking should go to the emitter connection of Q854).

This cap is located on the regulator section, and is part of the dual supply (probably +45v and -45v).
Voltage reading on the emitter of your problem is on the -50volt side.

check voltage on pin 1 of connector JJ07. (or emitter of Q853) it should read ~ +45vDC to ground
check voltage on pin 2 of connector JJ07. (or emitter of Q854) it should read ~ -45vDC to ground

I would expect your +50vdc will read OK, but your -50Vdc will be low, or not reading at all.

Most Likely defective parts
Q854 (most probable)
Q856
C861
C854
D850

If the DC voltages are showing correct (+45, and -45), I would look at the Driver power amp stages.

hope this helps
Tom

lwong2's picture

Please help my problem on Marantz 1180

Dear tom,

Thank you for your guidance and your time for checking up the circuit
I checked the e-cap polarity is correct(+ to Emiter).

Due to this problem (bass peak led lighted). I sent it to a repair technician and he replaced 6 pcs of the pre-amp transistors.( i paid $100 for the repair) . the replacements were :

Original part ( i believe were from Hitachi) replacement (substituted part)
QE 01 to QE 04 (p/n 2SA841) A933
QE 05 and QE 06 ( p/n 2SC1681) C 1815
After this replacement , the amp was tested for about 20 mins at the technician's shop. It worked ok .

I took it home and powered up. The same ( bass) peak led lighted immediately.
I opened the amp cover,checked and found the same cap bulged and leaked.
Problem not solved.
I have since replaced it ( a week ago) with a Panasonic cap 100uf 160 V. So far it worked OK after use for about 10 hrs.But the cap commence to bulge at the top. Another problem i observed was when the amp was on the left speaker ( woofer) was sucked in but the sound is OK.

I shall check as per your advice.As i hv not done any electronic testing i just bought a digital tester to learn something new to me.

Appreciate if you could kindly let me know if the above transisitor substitutes are appropriately used.

Thank you again for sharing your expertise, your time and kind help .

Best regards,

Wong

Please help my problem on Marantz 1180

Wong,
The parts (transistors) that the technician put in should be OK as replacements
Tom

lwong2's picture

Please help my problem on Marantz 1180

Thank you.

Please help my problem on Marantz 1180

Wong,
While I worked for Deutsche Bank, managing their data centers, I visited Singapore 3 times from 2004 to 2007. I loved Jumbo's seafood, the Long Bar, the Tiki bar on the East Coast Beach, Santosa Island, Orchid Street, Orchid Towers, the food, the people, and the country. I always had a great time when there.

I am using the Marantz 1152DC schematic/service manual available on this site to reference part numbers etc. I believe it is very similar to your unit, but some differences probably exist with transistor part numbers, and resistor values in the driver and output stages.

2 Things to look at.
The sucked in speaker on the left side is an indication of high DC coming from the output stage. This should be less than 5mv (.005 Volts) This could be a misadjusted DC balance pot, or a problem in the output stage. Check to voltage on the output and see if you can adjust it to "0" volts.
I believe the Variable resistor for the left side is R739. the right side should be R740.
Although the manual shows connecting meter leads between JN01 and JN05, you can just as easily connect to the left speaker terminals (+ and -), and adjust the potentiometer R739 for "0" volts. Do this adjustment slowly, as you will find it very sensitive. Then check and adjust the right side using Right speaker terminals and adjust R740. IMPORTANT: If you adjust R739, and you can't get the voltage to change, or you can't get it close to "0" volts, there is component problems in that output stage that must be fixed. IF YOU ARE ABLE TO ADJUST THE VOLTAGE TO "0" , AND THE HEAT SINK TEMPERATURE SEEMS THE SAME FROM THE LEFT AND RIGHT, THEN YOUR OUTPUTS ARE FINE AND YOU DON'T NEED TO CHECK THIS SECTION ANY FURTHER. A MISADJUSTMENT COULD BE CAUSING YOUR BASS PEAK LIKE TO COME ON.
Sansui used fusIble resistors in many of their units at that time, and they many times increased in value creating many problems. If you can't adjust "0" volts, shut the unit remove from power (unplug), and check the resistors using an ohm meter function. Compare the value from the left side to right. The type I have seen problems with are the small (1/4W, 1/2w) small value ones (1 ohm, 2.2, 4.7, 10, 22, 47, 100, 120ohm etc). You can usually check the in circuit without removing. Just make sure to test them both ways (+ and -, - and +), and use the higher resistance value.

As far as a 160v cap still bulging, make sure that this wasn't put in reversed. If you can, check the voltage across this capacitor. It should be low (below 15V,) and the + voltage should be on the + side of the cap. You need to get a new cap and replace it if you find the one in the unit was reversed. If it wasn't reversed, you need to replace again, and I would replace C854 as well because it could be putting a very high DC ripple on the regulator if it is open. Also check to make sure the 2 DC supplies are the same voltage (+45, - 45).

I think that the bulging cap, and speaker cone being sucked in are 2 distinct problems. The Bass peak light is probably caused by the DC balance misadjustment/problem. The bulging cap is another problem. The unit would probably work with this cap removed.

If you are able to fix the bass peak problem with the adjustment, and still have a problem with the bulging cap (it is probably overheating causing the bulging) You should then replace all of the electrolytics on the power supply section with ones of a slightly higher voltage rating (ie 470uf at 80v or even 100v, instead of the 63V). be careful of the polarity as you replace them.

Hope this helps
Tom

lwong2's picture

Please help my problem on Marantz 1180

Hi Tom,

First of all ,please accept my sincere thank you for you help. The actions you suggested are very detail and will look simple to an intelligent people but to me it
seems like climbing a high mountain. especially i worry i may cause more problems
Any way i shall try with care as to learn something new. Do you know if the transistors : C 1815 and A933 are suitable substitute parts for C1681 and A841 respectively.

Its great to hear that you hv visited Singapore . It has now a great change since you last visited here.I am quite sure that you wouldn't be able to recognize most of the places if you come again. We hv added 2 casinos , A theme Part at Sentosa, A flyer. Marina Bay Sands , Night safari at the Zoo etc etc etc . Also in Singapore , you will also find food , food , food every corner. All these are with God's blessing and provisions.The MRT transport systems will bring you every where you wish to go . Please call me if you are here the next visit so that we can meet and hv a cup of Tiger beer and some curry fish head etc etc. And also talk about hifi.

I hv some time now as i am just retired after working in 'Merck Sharp and Dohm'( pharmeautical) for more than 10 yrs. Prior to that I was working in General Motors Singapore.( Electronic ).

Playing with Amplifiers is my hobby since childhood.I hv some junks with me now like : Meridian pre101 and mono blks power 105 , Quad 44 , 405 , Quad 303 , 22 Philips A9016 , CD 100 , Marantz Cd 85 , Speakers like Tangent TM3 , Kef 105,4 , BMWs and many other junks etc.

One of my dreams now is, if i could bring in non working vintage amplifiers (tube or trans, Fisher or some reputable brands etc ) in bulk quantity preferably from UK or States , restore and sell them in Singapore.This is only possible if i myself is competent to analyse n trouble shoot . I think i need to look for a good tech n consultant in Sing to partner with.

Anyway sorry to bother you with all these nonsense.

Once again , thk you and best regards,

Wong

Please help my problem on Marantz 1180

Wong,
Good luck in your retirement. I tried retiring, and went back to audio repair as a hobby. I had been in the Air Force 1969-1973 repairing avionics on Aircraft. I was an audio Tech from 1973 to 1980+, but branched off into computers, and eventually managing data centers for large investment banks from 1985 to 2011. My retirement lasted only 1 year as I became bored at not working, even though I had fun restoring about 130 vintage units (Sansui, Pioneer, Kenwood, Akai, Onkyo, Sherwood, EV, etc) during that time.
I now do consulting for a large firm part time, and still work at times on my audio gear.

As for your problem, I would suggest that you test adjust the DC balance for your left channel to see if it gets rid of the Bass peak light. The adjustment pot can be found on the main amp board P700. Leave speakers disconnected, and connect your volt meter leads to the left speaker terminals. Turn unit on and adjust R739 for 0 volts plus or minus .005v. Then connect volt meter leads to the right speaker terminals and adjust R40 for 0 volts plus or minus .005v

And last but not least, shipping to Singapore from the US or UK is very expensive for these units, as they are heavy and need a lot of padding/protection, requiring the boxes to be large. Bulk shipping a lot of boxes is probably more cost effective, it will still be expensive. You may need to find a component level tech to help, as restoring units is a big job, requiring many parts (caps, pre am transistors, resistors, outputs, diodes, etc). Experience working on vintage electronics is almost a necessity, because as you stated, more damage can be done to these units by inexperienced people. (Especially solid state units)

I have found a copy of the 1180 Service manual, and will send it to this site for posting.

And yes, If I ever get back to Singapore, I will look you up. Keep the Tiger Beer cold, but I prefer the Chilli Crab rather than the curry fish heads.

lwong2's picture

Please help my problem on Marantz 1180

Hi Tom,

Thank you for your mail. I am glad that you can take spicy stuff -- like chilli crabs etc. My son's patents in-law are from Finland and station in Switzerland.They too love chilli crabs -- especially from JUMBO SeaFood restauraunt. Please don't forget to call me while you visit Singapore again.

Tom, I am very glad, getting to know you

By the way i manage to get a copy of the circuit diagram already -- thk you.

Best regards,

Wong

Please help my problem on Marantz 1180

just realized I referenced Sansui when I discussed fusible resistors. Marantz did have similar issues with some of their resistors on driver boards, but not as widespread as Sansui. Hopefully it is just an adjustment, and the peak bass light goes out.
Tom

Please help my problem on Marantz 1180

This is why some people don't think highly of techs. You need to get a refund or a proper repair from that guy. I've always stood behind my work, and that guy needs to also.

lwong2's picture

Please help my problem on Marantz 1180

Dear Johnnysan,

I lost trust in the repair job. It's quite difficult to find a reliable tech to trouble shoot on vintage equipments in Singapore. I am having doubt if the transistors that he changed on my amps are appropriate.I am trying to check from goggle to find if the substituted parts are actually relevant and not causing some other problems.

Thank you for your comments.

Best regards,

Wong