Jukebox amp rebuild or replace with modern amp

[Legtod2]

In the age of the solid state amp versus the tube amp I have been wavering on rebuild versus bolt on a new generation amp.

My nsm amp was built in 1984. The life span of its electrolytic caps are begining to show their age.
This also bring the question how many resistors and other items are begining to go out of tolerance.

I reviewed the list of all caps, resistors, diodes would be required and my list was long and expensive.

Then I went on line and reviewed the new generation amplifier boards that are available. These new boards have A, AB, D class amps with bluetooth at an affordable price. Imagine if you could simply connect your phonograph jack from the old amp and plug it into the new amp, connect the speakers and power and play.

Granted you may need a pre amp, or a board that has both amp and pre amp built in.

Has any one given thought to doing this ?

[Ken Layton]

All you'll need would be electrolytic capacitors. Your amp is new enough to already have modern metal film resistors in it. Those last forever and generally stay in tolerance. It also uses modern silicon diodes so no need to replace them either.

Don't forget that records are recorded and played back with the RIAA equalization curve:

https://en.wikipedia.org/wiki/RIAA_equalization

So if you simply plug the output of the tone arm cartridge straight into an amplifier, it's gonna sound funny. There are RIAA phono preamps out there which will not only preamp the tone arm cartridge to a "line level" output, but it will also apply the RIAA equalization curve to the signal so it sounds correct. The machine's original amplifier preamps the signal, applies the RIAA equalization, and amplifies the whole signal for distribution to the speakers. Don't forget the amplifier also has an important feature: MUTE. It mutes all sound during changing of the records and idle periods when the machine is just sitting there when finished playing records. The original amplifier also has remote volume control capability as well as output transformers which allow you to balance the sound level between the machine's internal speakers and any external speakers you might have connected. If you need "distributed" sound, it also has 70 volt output transformers. So you can see the original amplifier does alot of stuff and all you need to do is replace some old capacitors.

[ed12]

ya i thought worrie wort after the long post
caps yes "maybe", u have to understand these are german built machines and very tight tolrance
lord i would even have to question a weak tube
these things are like tanks,u can drive them hard and they love it
or soft and there just as
so i would just chk and see if the caps  are showing age >leakage-esr reading<
from there i would just enjoy it

ed

[Legtod2]

Thank you for your prompt replys...

My present amp has no hums or hissing sound. Just seems to be playing only the left side.

The msn amp utilizes different caps...

Ceramic, MKT, Tantal, and of course electrolytic.

If I were to replace just the 20 or so electrolytic caps then revisit the sound quality would I be any further ahead.

There are two mkt caps that seem ok but I am not sure about their life span.

[lilshawn]

We should really just be limiting age to about 15 years even if it tests as good... because after this time, the rubber plug that seals the bottom where the leads come out often starts to harden up and shrink about this time.

if you just straight replace them with whatever you can get, you will be revisiting replacing them in about 3000 to 4000 hours. (this is what modern capacitors are rated for in terms of stability in a perfect environment, so ball park less than that since even a 10C temperature rise due to the ESR will reduce the expected life by half.) cheap ebay caps probably 1000 hours or less.

choose your replacements wisely, not all capacitors are created equal.

[Legtod2]

Order placed with digikey.ca for just the electrolytic caps. I already have all my resistors on hand for any I find out of spec. Tried to order only long life caps time will tell. Fingers crossed this do the trick


Index   Quantity   Part Number   Description   Customer Reference   Available Quantity   Backorder Quantity   Unit Price CAD   Extended Price CAD   
1   2   P14424-ND   CAP ALUM 1000UF 20% 25V RADIAL      2   0   1.24000   2.48   
2   2   565-1564-ND   CAP ALUM 3300UF 20% 25V RADIAL      2   0   2.24000   4.48   
3   3   4788PHBK-ND   CAP ALUM 4700UF 20% 40V SNAP      3   0   8.69000   26.07   
4   5   P13148-ND   CAP ALUM 47UF 20% 63V RADIAL      5   0   0.74000   3.70   
5   5   493-14728-1-ND   CAP ALUM 10UF 20% 63V THRU HOLE      5   0   0.48000   2.40   
6   5   4137PHCT-ND   CAP ALUM 47UF 20% 40V AXIAL      5   0   5.04000   25.20   
7   3   4083PHBK-ND   CAP ALUM 2200UF 20% 63V AXIAL      3   0   7.16000   21.48   
8   3   4245PHBK-ND   CAP ALUM 220UF 20% 63V AXIAL      3   0   4.17000   12.51   
9   3   493-13371-ND   CAP ALUM 2200UF 20% 50V AXIAL      3   0   7.32000   21.96   
10   3   4141PHBK-ND   CAP ALUM 220UF 20% 40V AXIAL      3   0   4.90000   14.70   
11   5   P13146-ND   CAP ALUM 4.7UF 20% 63V RADIAL      5   0   0.51000   2.55   
12   5   493-1491-ND   CAP ALUM 100UF 20% 10V RADIAL      5   0   0.33000   1.65   
                  Subtotal   139.18
                  Shipping   0.00
                  GST   0.00
                  HST   20.88
                  PST   0.00
                  Total   160.06

[lilshawn]

Nichicon, panasonic, chemicon all tend to be really decent manufactures and make great caps.... but also the most duplicated. Highly sought after and high profile components are often counterfeit.

once they arrive scrutinize them and be sure you are getting what you pay for. I've even received fake components from reputable sellers like mouser.

I've had one time (and I posted it here, i just can't find the post) where someone resleeved the caps with a reputable cap manufacturer... but got part way though, got lazy and just put the good sleeve over a random name cap. you could peel the sleeve off and reveal the original random cap sleeve underneath.