[Music in a bottle]

I finally couldn't stand it any longer, and tore into my dual mono block Marantz model 15 from 1968! It had been making a mechanical sounding thump on power up, and I was concerned it was the power transformer in one of the modules. After an extensive process of elimination, I discovered that at least one of the two power electrolytic capacitors was dried up and needing replacement. For a guy with no electronics experience, I feel like rewinding the RF coils in my Philco 7o now! I still have yet to find 4 new caps that will fit in the space in my amps! They're unusual!

[Texasrocker]

Congrats music! Things that go "Thump" or,..."Hum",.. and other Things,.... that make you want to go "hummm" ,..show up in the strangest places sometimes!!! Enjoy your vintage Marantz! Im staying busy in what little spare-time I have to commit to the vintage-tube tech "hobby", that I highly enjoy on the sidelines of real-life,called my boring... ( day gig)! Im currently under construction,.. building (2) both,.. from "scratch",.. all tube compressor/limiters for a Rec Studio customer in Austin. Awaiting some "ultra-linear" specially built input & output transformers to arrive from the UK.Both trans exact replicas of the old vintage Peerless brand, that even the new owners of magnequest cant do unless I pay much more. Us co Jensen trans can build em, but the waiting list is much to long, ( very similar to the UK & Canadian healthcare systems)!! The Studio owners really liked my "prototype", so wish me luck in future success!?? Do you happen to know where I can find some pre-manufactured 3- space rack-type all aluminum ( pre-punched chassis for 4 minitubes, & ac trans cutouts?)anywhere on the net for under $75.? Any your suggestions would be appreciated indeed! Until then, my greenlees will have to do. Enjoy your Marantz, Ive owned several, and repaired many, of their vintage tube type hifi items in the past also!! I recently sold a (pair) Mc Intosh vintage C-8s ( tube pres) in pristine cond to a customer! Both still had all orig Telefunken tubes also! Lordy mercy,... tone tone maximus!! I also enjoy restoring vintage hi-fi!! Recheck your "thump-factor" on initial powerup in your Marantz, I dont think is was a bad cap causing that?, but I will standby just in case. Personally speaking, I would advise you to "hold off", on the Philco 70 chassis restoration until your sure your ready to tackle its full- electronic needs! 2 totally different "hobbys" indeed when restoring vintage 60s type integrated electronics items, than those of the 1930s era! Just my .02, however. Theres "books" out there, to read, & understand, ALL different types vintage electronics restorations! You can do it!! Enjoy your new tube-electronics hobby!! Finding good tube-techs are getting harder to find everyday indeed!! ol Tex

[Music in a bottle]

Frankly Texas, I will likely have my model 7o and my other philco, whatever model it is, rebuilt by one of you guys like Ron. I can build stuff, but cannot solder, and as it turns out, my Marantz model 15 caps wires are attatched with screws, so I can fix them THose caps by the way are presses up against the top cover and have a die electric blank over the tops to prevent shorts. When I hit the power with the covers removed, the thump is actually a buzz of power hitting the main electrolytics. I removed them, and replaced them with caps from my parts rigs, and now we are silent. I just need to locate new caps as I'm sure these are dusted too! These caps are 11,400 micros and stand nearly 5 3/4 inches tall and about 1 1/8 in diam. They each fit in a separate compartment, so sizing is somewhat touchy. The leads attach with screws. Love stuff from the 1960s! I do plan on getting a vintage tube outfit in the near future, probably going to settle with a set of marantz model 9s, because I just love the looks of the older marantz gear over mac, though I know full well, that mac gear is better.

[Arran]

Congrats music! Things that go "Thump" or,..."Hum",.. and other Things,.... that make you want to go "hummm" ,..show up in the strangest places sometimes!!! Enjoy your vintage Marantz! Im staying busy in what little spare-time I have to commit to the vintage-tube tech "hobby", that I highly enjoy on the sidelines of real-life,called my boring... ( day gig)! Im currently under construction,.. building (2) both,.. from "scratch",.. all tube compressor/limiters for a Rec Studio customer in Austin. Awaiting some "ultra-linear" specially built input & output transformers to arrive from the UK.Both trans exact replicas of the old vintage Peerless brand, that even the new owners of magnequest cant do unless I pay much more. Us co Jensen trans can build em, but the waiting list is much to long, ( very similar to the UK & Canadian healthcare systems)!!

I'm surprised that Hammond couldn't supply you with some output transformers, I do know that they make ultra linear inverse feedback types in the last catalog that I got from them, they also make them potted in a can if you so desire. Hammond will even custom build transformers of any sort, but needless to say it makes more sense if you have them built in quantity. Unlike the healthcare system, Hammond is a very efficient Canadian entity.
Best Regards
Arran

P'S I thought Jensen was a speaker manufacturer? I wasn't aware that they dabbled in transformers. Jefferson and Thordarson (if they are still in business) I know of but not Jensen.

[kruc]

Good find on those dried out caps there Chris. The internet is your friend when looking for unusual caps like you have in that chassis. AES, Digikey, Mouser, All Electronics, Fair Radio, Surplus Sales of Nebraska, and others I'm brainfarting about right now. Also there might be a yayhoo group dedicated to old Marantz gear. Just remember that electrolytic caps are polarized and will vent or explode if wired in reverse. Put a piece of tape or some other marker like a tie wrap to mark the positive lead. A lot of people have learned this the hard way.
Dave

[Texasrocker]

Music, I just noticed in your previous thread about the "thump" you are having on powerup of your model 15.
You stated, that you are "turning the amp on first" ..... then, turning on your preamp feeding the model 15?

Powerup your system in "reverse"! Always turn on your preamp first, then follow up turning on your amp secondly! "Thump" gone!! General rule of all-things in any type "component systems" hooked together.

The model 15s are very nice looking & sounding amps indeed! I repaired a mod 15 several yrs ago.If I remember correctly, Its basically 2 model 14s monoblocks in 1 cabinet? If so, it has a silicone type power supply?, and is prone to thermal-runaway. Keep your amp well ventilated when turned on! I may even still have a schemat here, but not sure. I do remember the large size caps. You can still find those if needed.

Bad capacitors go "humm",.... not "thump"!! Its always a good idea to change out the filter caps, especially due to age issues! However, your caps are still working fine unless you hear a "humm", especially since you have fired up the amp already, and let the caps charge themselves up since you purchased it.If the orig caps have changed orig shape anywheres, or look leaky on the ends,wait until you replace the electrolytic caps before using it on a daily basis. Bad electrolytics go "BANG" when they fry! Let off some nasty smelling smoke also!

The "thump" your hearing in your stereo system comes from "inverse powerup"... of turning your Marantz Mod 15 amp on 1st, then... turning on the power of your preamp feeding it!
Try turning on your preamp 1st,then your amp,.. betcha "thump" is gone!! Go stand-out in the sun for awhile,brighten-up abit,( just kidding music!) and get back to me? ( hee hee) ol Tx.

[Music in a bottle]

Thanks for the advice. you guys are awesome! Texas, yes they are 2 model 14's bolted together. The inside build quality reminds me of a ColIin's radio. There is no power switch on the model 15 and so I have it plugged into the preamp, switched receptacle. It actually wasn't a thump at all, but rather a buzz of electrical sound as the in rushing current hit the caps! The search has begun for replacements, and I located a guy who rebuilds model 15's and 16's only, so he might be able to line me up with these unusual caps. Will try to put up some pictures of the whole remodel, as this stuff fascinates me!

[Music in a bottle]

Good find on those dried out caps there Chris. The internet is your friend when looking for unusual caps like you have in that chassis. AES, Digikey, Mouser, All Electronics, Fair Radio, Surplus Sales of Nebraska, and others I'm brainfarting about right now. Also there might be a yayhoo group dedicated to old Marantz gear. Just remember that electrolytic caps are polarized and will vent or explode if wired in reverse. Put a piece of tape or some other marker like a tie wrap to mark the positive lead. A lot of people have learned this the hard way.
Dave

These I think are going to be hard to nail down because they are super skinny and tall and fit into holder compartments! Wish me luck.

[codefox1]

Some transistorized preamps have an output capacitor that can send a DC charge to the following amplifier, abd sometimes they shorted, and some power amps have no input capacitor that will nullify the defect. So, you can turn the preamp on first, then the amp and not get the thump which can still easily blow out a speaker. You can wire in a capacitor between the input jack of the power amp and it's first stage of amplifiation. And just what value should you use? The answer is "it depends." I would personnally start with an .05 mfd 620 volt and see how it sounds. I assume that both machines have, or have been converted to proper 3 wire grounded recepticles, and the "death capacitors" have been removed. Use crap speakers and resistive loads in parallel when trying out these tests, and let us know what you find.

[Music in a bottle]

Some transistorized preamps have an output capacitor that can send a DC charge to the following amplifier, abd sometimes they shorted, and some power amps have no input capacitor that will nullify the defect. So, you can turn the preamp on first, then the amp and not get the thump which can still easily blow out a speaker. You can wire in a capacitor between the input jack of the power amp and it's first stage of amplifiation. And just what value should you use? The answer is "it depends." I would personnally start with an .05 mfd 620 volt and see how it sounds. I assume that both machines have, or have been converted to proper 3 wire grounded recepticles, and the "death capacitors" have been removed. Use crap speakers and resistive loads in parallel when trying out these tests, and let us know what you find.

I'm using a model 7t marantz, and I need to look at the schematics of the amp, but I believe the input dumps into a capacitor. By the way guys, the thump I was hearing, is actually a loud audible AC buzz that instantly went to a hum, then silent. The sound was noticeable at the main electrolytics, and never came through the speakers. Since I changed the caps out with a set from one of my parts rigs, the amp still makes that sound, but not nearly as often. Probably 1 out of every 6 times now. Would it be wise to simply plug it into the wall recept, several times to see if I can figure out if it is the preamp? My preamp has outputs for an osc. which I have one hooked up, and at power up, there is no visable trace on the scope other than the flat line of the sweep. I also had the scope hooked to the numerous amplifier outputs, with no spike or fluctuation of the flat line sweep, again. According the original literature that I got with these amps, the caps are phone company grade. What are the chances of getting replacement caps that have these same characteristics with threaded post's for wire hook up, like the originals? If you have never seen vintage marantz gear, you should treat your eyes. They are real works of art in my opinion, much like the old Philco radios! I'll try to get some photos up here for you all to view.

[kruc]

Finding caps with threaded terminals isn't difficult. Look at the sites I mentioned above, also check Allied. These days the standard is called computer grade. You didn't mention the voltage you need. I did a quick check at Digi-Key and pulled up 27 caps at 12,000uf with screw terminals at ratings between 10 and 450 volts.
Dave