I got a Fisher Price #816 battery-powered phonograph from 1983. It played fine for a week and then the speed started to intermittently increase to “chipmunk” without warning. Moving the volume control to certain positions also effected the speed. No fun! A few years later, the sound kept cutting out intermittently. Where’s the fun in having a Sesame Street record player if the cartridge won’t work? Here’s what I did to fix both problems:
Fixing The Speed
I took it apart and found that the player has an electronic speed control, with trim-pots to fine-tune the 33 1/3 and 45 rpm speeds (VR1=680Ω, VR2=5kΩ). When I poked at the trim-pots the speed went crazy. They were probably oxidized. I marked their positions and swept them back and forth a few times to clean their tracks. That totally fixed the speed problem so I returned them to their marked positions. I recommend using a strobe light (or any neon lamp) and a printable strobe disc to re-calibrate the speeds. UPDATE: Every year or so the speed problems returned (fixed by cleaning the pots) so I eventually replaced them with modern multi-turn trimmers. (blue ones in photo) I used these values: VR1=1kΩ, VR2=10kΩ and had no problems calibrating the speeds accurately.
The other battery-powered Fisher Price record players have the same internals as this one, so if your Fisher Price #820 or Fisher Price #3814 have speed problems then you might have dirty trim-pots. If you have the AC-powered Fisher Price #825 then this won’t help. (Those players have a simple tire-driven mechanism with different sized idlers for each speed. There is no electronic speed control.)
Auto Shut-Off
I was surprised to find that my player had an internal switch that was activated when the tone-arm moved to the lock-groove at the end of a side. Strangely, this switch had no effect on the motor or amplifier (Instead it spun endlessly, depleting the battery). I’m not sure what this switch was intended to do, so I jumpered its pads on the PCB and rewired it as a power cutoff. The pictures on this page shows the wiring before my modification. (Sorry, I didn’t document it.)
Fixing the Intermittent Sound
At first I thought it was just a scratchy volume pot, but cleaning didn’t help. Then I cleaned the contacts on the socket where the cartridge mounts to the tone arm. That didn’t help either. I got a replacement cartridge (Pfanstiehl 911-D7) but it didn’t make any sound at all! Clearly something was wrong with those contacts so I took apart the tonearm to get to them:
(It will be limited by the length of the delicate tonearm wires. You can do this repair without disconnecting them, but it’s easier/safer to desolder them and put them back when you’re done.)
(I have the #816 Sesame Street version. Perhaps the normal #820 version uses screws instead?)
(These pictures show the clips after my modification. I didn’t take “before” photos.)
Further Resources:
This Old Toy has info about Fisher Price phonographs
This thread on Audio Karma has more photos of the interior of a Fisher Price #816
This thread on Antique Radio Forums has photos of the interior of a Fisher Price #820
The Portable Record Player Breakdown from Flea Market Funk summarizes battery powered phonographs