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1973 1617-1

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Buckie
Posted 2019-03-10 10:06 AM (#547293)
Subject: 1973 1617-1


Joined:
February 2019
Posts: 8

Recently purchased my first Ovation. It appears to be pretty original. Someone did string it left handed and had to replace the nut. Removed the electronics to inspect everything. Battery box was corroded from battery being left in for years. I was able to make parts to repair as a terminal was corroded off. Couple tuner were sticky and disassembled and cleaned. Little stuff like that. My major issues I have is nothing from the electrons and wondering if anyone would have any ideas on trouble shooting or have worked on these.

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BCam
Posted 2019-03-10 11:18 AM (#547294 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
October 2014
Posts: 193

I don't have any experience with this particular unit but the first thing you need to determine are:

1) Is power actually getting from the battery box to the pre-amp?

2) Is the problem is with the pickup or the preamp? The easiest way to determine this would be to plug in another pickup. I would think that even a generic, inexpensive piezo pickup would be sufficient. Even if it's not a great match, you should get some sound out of it just by tapping it.

3) Failed or dirty switch/control. Try an appropriate spray contact or fader cleaner first. If that doesn't fix it, you can check it out with a multimeter.

4) Check your output jack and make sure it's making the appropriate contact to your 1/4" plug and there's continuity from the jack to the pre-amp.

If none of the above is the problem, you'll need to check out the preamp itself. You are fortunate that the preamp is as old as it is since repair is easier than on more modern units. It's akin to part of an old transistor radio. If you're not up to it maybe you can find a friend (or a friend's kid) with basic soldering and electronic skills. Most of us would grab on to a project like this with glee.

1) The first thing I'd do is to remove, clean and re-install the two screws holding the PCB (printed circuit) board. Often, mounting screws like these provide a ground connection between the PCB and the case.

2) if that doesn't work, you'll need to remove and inspect the board, its solder points and components. After removing it, I'd give it a good cleaning with Q-Tips and isopropyl alcohol. The likely suspects are:

a. "Cold" or failed solder joints that need to be re-soldered. (Google "cold solder joint" )
b. Failed capacitors. These may or may not show visible signs of leakage or swelling and are the most common parts to fail with age. (Google "bad capacitor" )
d. Failed transistors or other parts.

I've brought a couple of guitar amps and several ham radios back to life by doing nothing more complex than cleaning, re-soldering a couple of connections and replacing a capacitor or two.

All parts should be identifiable by a number or color code and replacements should be available from stores like Fry's Electronic or online stores like Mouser. If you're lucky you may even have a local electronic parts store (RIP Radio Shack). You have the PCB so, even a complete re-build would be within the skill set of most beginning electronic hobbyists and probably wouldn't cost more than $25 or so for parts.

Of course, you could always replace the unit with something more modern but where's the fun in that?



Edited by BCam 2019-03-10 11:35 AM
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Buckie
Posted 2019-03-10 11:53 AM (#547295 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
February 2019
Posts: 8

Wow thanks for a great responce. Very detailed. I do like tinkering and fixing things. See where I get. I do prefer to keep things original as possible like an old classic should be. Just want it to work like it should, lol.
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BCam
Posted 2019-03-10 3:16 PM (#547297 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
October 2014
Posts: 193

And also check out the connections, jack, etc. between the pickup and the preamp. I think you'll have fun with this.

Edited by BCam 2019-03-10 3:17 PM
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Buckie
Posted 2019-03-10 6:32 PM (#547299 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
February 2019
Posts: 8

I actually installed that 3.5mm jack between the preamp and piezo pick up you see in pictures. Pretty simple and I tested the solder connection before reinstalling with multimeter. I had to cut that wire in order to remove the piezo from guitar. Believe it or not they don't use the mini jacks in 73 and must of made this soldered connection on the guitar, direct connection to the preamp. Wasn't sure if i should of used a 2.5mm jack but any mono jack is hard to come by. Where's Radio Shack like places now. Anyways, I'm sure I'll figure this thing out. It does sound amazing even without amplification. Thanks again for the insight.
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BCam
Posted 2019-03-11 4:54 PM (#547310 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
October 2014
Posts: 193

If you've done that, you have the skills for a complete rebuild should that prove necessary. The traces look good on your PCB but you might want to check them for continuity as well. If there are any gaps you can bridge them with solder.
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DanSavage
Posted 2019-03-11 7:00 PM (#547311 - in reply to #547299)
Subject: Re: 1973 1617-1



Joined:
June 2012
Posts: 1940

Location: Lake Forest, CA
Buckie - 2019-03-10 4:32 PM

I had to cut that wire in order to remove the piezo from guitar. Believe it or not they don't use the mini jacks in 73 and must of made this soldered connection on the guitar, direct connection to the preamp.


I never knew that, either, until I went to pull the saddle out of my early-70s 1613 and found I had to pull the whole system.
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BCam
Posted 2019-03-12 1:22 AM (#547312 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
October 2014
Posts: 193

Let us know how this turns out and post some photos of the other side of the PCB. Good luck.
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numbfingers
Posted 2019-03-12 9:23 AM (#547317 - in reply to #547293)
Subject: RE: 1973 1617-1


Joined:
January 2006
Posts: 1081

Location: NW Washington State

Here are three schematics that might be similar to your preamp:

Related image

 

 

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numbfingers
Posted 2019-03-12 9:32 AM (#547318 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
January 2006
Posts: 1081

Location: NW Washington State
If you have experience working on PCBs, you might consider replacing the 4.7 or 5 uf electrolytic capacitors while you have the preamp out (if yours is like the schematics). Not sure if these old capacitors have have been a problem in these preamps.

-Steve W.
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jay
Posted 2019-03-12 10:21 AM (#547320 - in reply to #547293)
Subject: Re: 1973 1617-1



Joined:
January 2009
Posts: 1223

Location: Texas
I recall one other thread on this forum from a guy that spoke (over my head) about having to repair a board. You might try searching the forum for that thread.
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BCam
Posted 2019-03-12 11:52 AM (#547324 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
October 2014
Posts: 193

A de-soldering tool will help remove parts from the PCB.

https://www.homedepot.com/p/Aven-Desoldering-Pump-with-ESD-Safe-Plas...

And, I agree with Steve W. in that replacing the electrolytic capacitors is worth doing even if they look OK. I once met a guy who worked for a company repairing office phone consoles and he told me that the majority of their repairs involved capacitor replacement. If they haven't failed yet, they will.
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Buckie
Posted 2019-03-12 7:15 PM (#547331 - in reply to #547293)
Subject: Re: 1973 1617-1


Joined:
February 2019
Posts: 8

Thanks again to all for the great information. Will update when I get this thing solved. I agree with the capacitor issue, its usually first thing that goes wrong with vintage tube amps. An when that happens it's disastrous.
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