• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer Spec 1 Pre-Amp Sound Issue

xXColdShotXx

xXColdShotXx

Active Member
I am storing my uncle's spec 1 and spec 2 components. I decided to hook up the spec 1 since he said something was wrong with it. I wanted to see what it sounded like. The left channel works pretty good, but the right channel barely plays and fades out if you mess with the bass, treble or volume. I used it as a pre-amp only hooked to my yamaha mx-800/u. The volume, pots and switches need cleaning. The spec 2 supposedly works fine, haven't hooked it up yet. Anyone have a guess what might be going on with the right channel of the spec 1? Thanks in advance.
 
Register to hide this ad
I finish restoring one last week. It had different issues.
What does it do with the tone defeat?
 
When I turn tone switch off it just cuts off the bass and treble, still has a little bit of audio coming through.
 
Last edited:
Very hard to say at this point.
A thorough Deoxit treatment is in order before any real troubleshooting is done.
Barring that statement, every Spec 1 I've done has had a different issue.
Basically, it could be anything.
There's several problematic transistors located on each board and should be replaced with new equivalents.
The input board has been a source of issues on a few with one channel not working but this is only a guess. It's fairly easy to check for the signal through the input board.
 
Thanks for the info. I have some deoxit. I'll ask my uncle if it'd be ok to clean the pots and switches first. Could a person loosen the volume screws enough to get deoxit in there without taking a chance on messing anything inside up?
 
Tracing the signal through the pre is the best approach. If it appears to be the volume control, deal with it at that point. No need to open a can of worms.
Deox the controls first, then trace the signal through the set. Find where it gets lost. Repair and consider replacing the old transistors.
 
I cleaned the spec 1 controls with deoxit and they work a lot better. the right channel doesn't cut out anymore and plays, but doesn't have the bassy thump like the left channel.

I checked all the tape and aux inputs, they all have the same music output.
 
Last edited:
Just hooked the spec 2 up and let it play for around 10 minutes, then all the sudden I hear a small pop and smell something get hot, then I noticed the right meter was almost on 500 and the protection light was on. I had a yamaha cx-600/u pre-amp hooked up to it and it was playing just fine on both channels until that happened.
 
Hey Zebulon, would you happen to know an alternative to 647-UKL1H010KDDANA? On mouser it says non-stocked. It's the only one on the spec 1 bom list that way. Thanks in advance.
 
505-MKS2B041001C00JS - Film
647-UKL1H010MDDANA - Aluminum Electrolytic
 
Thanks, Zebulon. Is there a resistor and diode spec 1 list around? I also need a spec 1 power light bulb replacement # if there are any.
 
Last edited:
I saw a post one time on the lamp. An LED I believe. See the scat, it may lend a clue to the voltage requirements.
 
You can check for service the diodes and resistors. No need for a preemptive order.
Are you capable of this level of repair? Tooling, industry knowledge?
 
I have changed a few in my sx-1250, but it's been a while since then. Would a bad cap or transistor cause the spec 2 to go into protection mode with the right meter almost maxing out when I turn it on now?
 
You must log in or register to reply here.
Back
Top Bottom