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Wurlitzer 1700 low volume
Posted: Fri Mar 27, 2015 9:03 am
by juker
I have a Wurlitzer 1700 with low volume. The amp has been recapped. I'm using a known good cobra that works well in my other Wurlitzers.
To see if there was a problem in the amplifier I took a RCA plug and attached short clip leads to it. I then clipped them to the cartridge and plugged it directly into the amplifier. I'm getting loud noise when gently rubbing my finger over the stylus so I know the amp has plenty of volume. Next I checked the wiring up to the mech socket and it checks out with an ohm meter. The problem seems to be between the cartridge and the plug mounted on the mech.
Do the cartridge sockets ever give problems as the wiring seems to be fine. The contacts in the socket look shiny and clean. Any help would be appreciated.
Re: Wurlitzer 1700 low volume
Posted: Fri Mar 27, 2015 4:06 pm
by Ron Rich
You have triggered a memory, but I can't seem to recall exactly what I found, regarding that situation--- I THINK that I wound up replacing the wire/plug, going from the amp to the tone arm, bi-passing the socket mounted to the chassis. HTH Ron Rich
Re: Wurlitzer 1700 low volume
Posted: Fri Mar 27, 2015 4:15 pm
by MattTech
Mute switch adjustments?

Re: Wurlitzer 1700 low volume
Posted: Fri Mar 27, 2015 4:27 pm
by Ron Rich
Matt,
I doubt that--mute switch is an over-center, snap action switch--never saw one "allow" low sound---

Ron Rich
Re: Wurlitzer 1700 low volume
Posted: Sat Mar 28, 2015 3:45 am
by Rob-NYC
It is an RF cable and anything that adds capacitance will change the output.
Look for "knuckles and sharp bends.
The Cobra system uses a simple-cheap form of FM known as Slope Detection. The cart which is just a coil and metal vane is placed in the oscillator tank circuit. Sound is produced by pulling the oscillator off frequency. As with regular FM, the frequency of deviation determines the frequency of the reproduced signal and the degree of deviation determines the loudness.
If excessive capacitance in the cabling or socket is introduced or the tube gets weak it can reduce the system's ability to follow the fluctuations in the audio.
Try another cable. A piece of RG 59 from a cable TV install will work, but even a composite video cable is more than adequate for a test and replacement.
Don't overlook the possibility of a weak oscillator tube.
I've owned three 1800's and a 1700 along with a few later Cobra equipped models. I converted all to magnetic pickups. It is a bigger job on the 1700 and 1800 arms but the difference in quality and record wear is well worth it.
Rob-NYC
Re: Wurlitzer 1700 low volume
Posted: Sat Mar 28, 2015 4:44 am
by Ron Rich
I just remembered what I found once ( my great but not to long memory is running at Microsoft speed today)-Poor connection(s?) in the cartridge socket, caused it----Deoxit !! Ron Rich
Re: Wurlitzer 1700 low volume
Posted: Sun Mar 29, 2015 8:41 am
by juker
Thanks for all the replies

I'll try cleaning the socket tomorrow and if not I'll replace the wire.
First thing I thought of was the muting switch but the amplifier works at full volume with a short 14" lead from the input plug on the amplifier to the cartridge so it was ruled out.
You may have something here Rob with the short bends in the wiring. The cable makes its way through a couple sharp bends. I'll see what I can find out.
Re: Wurlitzer 1700 low volume
Posted: Sun Mar 29, 2015 8:47 am
by juker
I had checked all the tubes when I rebuilt the amp but I will recheck the 6J5 oscillator. I'll convert this one to a magnetic cartridge too when I get the time.