N
notCardio
I walk the line
Cool! I've got an old Marantz amp from the same era, but one side's blown. Looks like I finally found who to send it to.
dragonworks
Banned
Well, don't jump the gun, lets see if I can fix this one. Opened up the bottom last night and one of the large filter caps is burnt so I will replace those to to start with. She turns on, doesn't smoke or anything, but no sound.
E
ecc83
Well-known member
DO NOT! Connect any speakers to that amplifier (well, none you value!). Instead connect a DC meter to each output and look for an "offset voltage". There should be none or very little, an acceptable level would be 10mV or less.
Do you have a schematic? If not you will not get far.
Dave.
Do you have a schematic? If not you will not get far.
Dave.
dragonworks
Banned
I have the schematic, the repair manual and the owners manual. this thing has some real problems. I once set a good speaker on fire, I have learned my lesson.
E
ecc83
Well-known member
Heh! Been there! Got the T shirt. 30 odd years ago I struggled to re build these old DC coupled amps, not Marantz but Sony, Hitachi, Ferguson...If you want the amp for your own use it is often far easier to strip out the old PA section, fix the PSU and lob in a couple of modern power amp modules.
Dave.
dragonworks
Banned
I am just looking to learn more.
E
ecc83
Well-known member
Err? Do you mean you would like to learn more about fitting modules or just "everything in general"?
Dave.
DM60
Well-known member
This is an old late 70's receiver. Not sure if these were sold in the US, but when I was in the military, they sold these in the PX. I had a set of Marantz Speakers, made in France! This is a nice system if you can get it to work.
That is 130 watts that can be actually used.
That is 130 watts that can be actually used.
dragonworks
Banned
it was built in the United States from what it says on it.
---------- Update ----------
in general
DM60
Well-known member
For reasons unbeknownst to me, I always thought this was a Japanese firm. But I never really looked. They were, at the time, consider a very good receiver as were Pioneer, Kenwood, Phase linear can't remember the rest.
E
ecc83
Well-known member
Yes, I too would have said Japanese at first but then this med ridden old brain dredged up something that said "America"!
Other top makers were Sony (their really top end stuff, same for Hitachi) Denon, Yamaha, (what DIDN'T they make? And all bloody well!) Kenwood became/took over/were taken over by Trio.
Over here Revox made some good stuff including what was probably the best FM tuner ever built (or was that Karlesberg?) . Quad of course, Radford* tho' they never soiled their production lines with a "receiver"!
*Got a Wayne Kerr Radford noise meter, super thing.
Dave.
dragonworks
Banned
pulled both amps out, one of them has a few burnt components on the board. Some one has been in there, the transistors are different makes between the left and right amps.
E
ecc83
Well-known member
Ok, so that eliminates any possibility of a "vintage" restoration. I would look at ILP 120W modules!
Dave.
dragonworks
Banned
I can probably repair the board, will go at that first. Replace the output transistors and the drivers and a few caps and resistors and see whats up. This will take some time. Have to track down the substitutes etc, and then there is the money involved. The power supply seems to be working okay, don't know about the protection circuit, will replace those caps and the relay.
E
ecc83
Well-known member
Replace ALL the transistors in the power amps! Sony used to send us "kits" when we asked for just output transistors for their amps. You just need one of the beasties to be leaky and FRAPPP! Bloody lot fries again.
Oh and the early protection circuits didn't!
Dave.
dragonworks
Banned
I have had to bypass the traces and go point to point on some boards in the past.
dragonworks
Banned
bought a set of 8 output transistors, 40 bucks.
E
ecc83
Well-known member
Ok, well if there are fuses in the DC power lines replace them pro tem with 100mA types. If there are no fuses, get some fusecarriers and fit them!
When the work it done I STRONGLY advise you to run the amp up on a Variac, if you can't beg or borrow one at least put a 60W incandescent lamp in the mains circuit and run the amp up with a meter hooked to show offset voltage and if possible one measuring quiescent current.
Best of!
Dave.
dragonworks
Banned
if I can get it up and running it goes up on ebay, they are going for better than five hundred dollars. The transistors are wire wound, not soldered, I have never had to get them off, how does one go about it?