Machineghost
Ghost in the machine
Whoa - thats a detailled restoration you are doing there. Well done!
Marantz 2500 Refurb
- Thread starter rBuckner
- Start date
Outstanding work there neighbor. I'm starting to think that your friend isn't going to sell this one.
After listening to a rBuckner Marantz refurb he may indeed decide that it's a "keeper".
Looking good Randy....you have a real talent:thmbsp:
Time to do the adjustments!
Power supply: check
Amp adjustments: check
Scope adjustments: check, I think. The tuner/multipath ones are weird.
AM alignment: check
FM alignment: Uh oh! I knew the performance was poor but assumed a bad alignment. No such luck, see the battle below. The multiplex / separation adjustments went fine however.
There's a few errors which I'll also report in the manual error thread. The amp bias pots are R761, the manual says R716. The 19kHz test point is J236 not J238.
First some pix. You have to remove the Dolby adapter housing to get at the tuner adjustment holes, what a pain! Not to mention there's no guide to what each adjustment point was on the front end. Thankfully it was pretty much like all other Marantz ones. You can see I started to sketch out which was which and I'll have to complete that and post it.
After removing the shield off of the huge all-in-one tuner board, I rechecked my electrolytic cap replacements for polarity and solder bridging and found none. I went ahead and shotgunned the 10.7MHz filters as I've seen them be bad before, but no luck. Here I set up a 2270 and used a piece of RG-174 cable and connected the front end's IF output on over to the 2500, it worked nice! Just to verify I connected the 2500's IF over to the 2270 and it was sucky. So it's somewhere from the antenna terminals to the output of the front end. I checked the coax cables to be sure they weren't shorted out.
I fooled around quite awhile with the antenna wiring, the 300 ohm balun and such. Ineterestingly it worked much better with the antenna input removed from the front end and just a single clip lead on the antenna input. I hooked up my FM generator and really got just as poor performance as before so I suspect it's just an anomaly of the real issue. But RF can do weird stuff and we used to joke that it stood for "Real Fun" although there's other more bawdy ones!
SO it was time to pull the front end out to see if there was some bad soldering or anything visible. First the tuner string was taped down to keep it in place.
Then it was flipped over. I didn't find anything cracked or funny looking. I resoldered the whole board but it didn't help at all.
So I did much searching on the 3 MOSFETs in the front end, the 3SK59's. There is an NTE222 sub for it but Ceitron claims to have the 3SK's so I will try ordering them and see what I actually get!
This is depressing as I thought I was nearly done outside of once again replacing the fan and the underrated power resistors for the fan and the slow start. For sure it's not like a spare front end for one of these is going to pop up! Sigh - so it'll be a few days before another update.
Power supply: check
Amp adjustments: check
Scope adjustments: check, I think. The tuner/multipath ones are weird.
AM alignment: check
FM alignment: Uh oh! I knew the performance was poor but assumed a bad alignment. No such luck, see the battle below. The multiplex / separation adjustments went fine however.
There's a few errors which I'll also report in the manual error thread. The amp bias pots are R761, the manual says R716. The 19kHz test point is J236 not J238.
First some pix. You have to remove the Dolby adapter housing to get at the tuner adjustment holes, what a pain! Not to mention there's no guide to what each adjustment point was on the front end. Thankfully it was pretty much like all other Marantz ones. You can see I started to sketch out which was which and I'll have to complete that and post it.
After removing the shield off of the huge all-in-one tuner board, I rechecked my electrolytic cap replacements for polarity and solder bridging and found none. I went ahead and shotgunned the 10.7MHz filters as I've seen them be bad before, but no luck. Here I set up a 2270 and used a piece of RG-174 cable and connected the front end's IF output on over to the 2500, it worked nice! Just to verify I connected the 2500's IF over to the 2270 and it was sucky. So it's somewhere from the antenna terminals to the output of the front end. I checked the coax cables to be sure they weren't shorted out.
I fooled around quite awhile with the antenna wiring, the 300 ohm balun and such. Ineterestingly it worked much better with the antenna input removed from the front end and just a single clip lead on the antenna input. I hooked up my FM generator and really got just as poor performance as before so I suspect it's just an anomaly of the real issue. But RF can do weird stuff and we used to joke that it stood for "Real Fun" although there's other more bawdy ones!
SO it was time to pull the front end out to see if there was some bad soldering or anything visible. First the tuner string was taped down to keep it in place.
Then it was flipped over. I didn't find anything cracked or funny looking. I resoldered the whole board but it didn't help at all.
So I did much searching on the 3 MOSFETs in the front end, the 3SK59's. There is an NTE222 sub for it but Ceitron claims to have the 3SK's so I will try ordering them and see what I actually get!
This is depressing as I thought I was nearly done outside of once again replacing the fan and the underrated power resistors for the fan and the slow start. For sure it's not like a spare front end for one of these is going to pop up! Sigh - so it'll be a few days before another update.
catrafter
Marantz Specialist
Using a sub front end is a great way to troubleshoot FM sensitivity issues. I have a front end out of a junk receiver that I can patch in.
I'm chasing an issue with the scope on my 2500 restoration, audio looks great but nothing is displayed when the tuning or multipath button is pressed.
I hate to take the front off again!
Tom
I'm chasing an issue with the scope on my 2500 restoration, audio looks great but nothing is displayed when the tuning or multipath button is pressed.
I hate to take the front off again!
Tom
catrafter
Marantz Specialist
Well, I've got it half working, there was a bad joint on the PR50 board, throwing the beam off the top of the CRT when the Tuning button was pressed.
Still looking into why H centering shifts when the Multipath button is pressed.
What a pain!
Tom
Congrats on getting it working again. :thmbsp:
Thanks dj, the encouragement is appreciated. Mostly it's many years of experience being shared by us tech types because it's fulfilling to help others.
On the parts acquisition front, I have the new ball bearing fan and power resistors. The transistors were sent 2 day priority two days ago aaaaand didn't get here today. They are on the way from Phoenix though so I should have them tomorrow. Our mail delivery is funny as it might be 10AM or all the way at 5:30PM like today. I still appreciate the job USPS does for the small charge they ask though, and our local postal workers are just the BEST! Stay tuned!! (Bad pun intended :sigh
On the parts acquisition front, I have the new ball bearing fan and power resistors. The transistors were sent 2 day priority two days ago aaaaand didn't get here today. They are on the way from Phoenix though so I should have them tomorrow. Our mail delivery is funny as it might be 10AM or all the way at 5:30PM like today. I still appreciate the job USPS does for the small charge they ask though, and our local postal workers are just the BEST! Stay tuned!! (Bad pun intended :sigh
diddlybopper
Super Member
The chassis was then blown out with compressed air and then washed.???
What do you mean washed and what did you use to wash.
What do you mean washed and what did you use to wash.
Great question! :yes:
Washed with Windex and scrubbed with an old toothbrush, resprayed and blown out again with compressed air. Not everyone agrees with this method! I did remove the scope tube first. It then air dryed for at least 3 days before any power was applied again. As this can run crud into depluggable boards those connectors were cleaned with alcohol, pins rubbed with a pencil eraser and "painted" with DeOxit to protect them and plugged in and out several times while the DeOxit was wet to get some on the socket sides.
Washed with Windex and scrubbed with an old toothbrush, resprayed and blown out again with compressed air. Not everyone agrees with this method! I did remove the scope tube first. It then air dryed for at least 3 days before any power was applied again. As this can run crud into depluggable boards those connectors were cleaned with alcohol, pins rubbed with a pencil eraser and "painted" with DeOxit to protect them and plugged in and out several times while the DeOxit was wet to get some on the socket sides.
diddlybopper
Super Member
Thanks for the reply.Another highly regarded tech here mentioned Glass Plus so that's what we'll do.My latest buy a Marantz 2285B looks like it's spent it"s life in a smoking room.Dish soap didn't touch the nasty looking faceplate but a product available at my dollar store called "Awesome" and it is,cut thru it like butter.Best dollar I've ever spent.
I squeezed in enough time to replace the first MOSFET in the front end. The tuner drum and cord was all taped down and the station I was on was a strong local one and a test with all the covers off and a single clip lead right on the antenna terminal came in in stereo and the multipath scope display was up nice and high on the screen. That was a false hope.
I reassembled the tuner's cover and got it mostly back in place, antenna coax from the back panel reattched and now it barely works! I took off the antenna coax and retried the clip lead and it barely works better. So something is very weird and/or the transistor I put in was blown to begin with. It came in an ordinary plastic bag with no wire grounding thingie around the leads. Hmm. Thankfully I didn't toss the old part and put it in the same anti-static bag I put the other new parts in. So it will come back out when I have time again which may not be until Monday night and we have company coming again next weekend.
My Christmans wish / gift I'd like this year is more time!! Sorry for the whiny passage, I'll put on my Superman undies and get over it!
I reassembled the tuner's cover and got it mostly back in place, antenna coax from the back panel reattched and now it barely works! I took off the antenna coax and retried the clip lead and it barely works better. So something is very weird and/or the transistor I put in was blown to begin with. It came in an ordinary plastic bag with no wire grounding thingie around the leads. Hmm. Thankfully I didn't toss the old part and put it in the same anti-static bag I put the other new parts in. So it will come back out when I have time again which may not be until Monday night and we have company coming again next weekend.
My Christmans wish / gift I'd like this year is more time!! Sorry for the whiny passage, I'll put on my Superman undies and get over it!