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Problem with SX-1250

L

Larry S.

New Member
Hello from a newbie,
I'm very happy to be aboard and glad I found this forum. Hope this is not something that repeatedly asked ?
When approaching one half volume (although not hearing any noticeable "clipping" or distortion) the receiver momentarily "cuts out", comes back on, and "cuts out" again until the volume is lowered? Seems like it will make it a little further up the volume scale with the high filter engaged. Is there a simple test that can be run on the speaker connectors with a volt meter ? Could it be a speaker problem ? I have two LBL L-166's and two JBL L-112's connected. The foams need replacing on one of the L-166's
I really would like to bring thing to someone who works on vintage Pioneer and just go completely through it. Any recommendations would be greatly appreciated..
Thanks
 
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Welcome Aboard!

If the speakers are at least 8Ω or are used only one pair at a time the unit should be able to power them unless there is a wiring problem or damage to the speakers/crossovers. Speaker resistance can be checked with your ohmmeter when disconnected from the unit. 8Ω impedance speakers will typically exhibit at least 6Ω DC resistance. Lower than that might indicate problems.

Presuming the speakers are verified intact, there are several things which can be checked and potentially a few adjustments which can be made. DC offset of the output amplifier stages can be checked and adjusted. Quiescent or idle current of the final output drivers can be checked and adjusted if necessary.

However, before any of that happens it will be necessary to obtain a copy of the service manual and diagrams. The layout, schematic details, and procedures are all described in the manual. Before checking the offset and idle current the power supply voltages need to be checked. This requires measuring voltages in the unit in some rather congested locations. Caution must be exercised to prevent personal injury and/or damage to the unit. Voltmeter probes should be insulated all the way to the tips to prevent inadvertent shorting. If opening the unit and performing several measurements is not an option the unit should be professionally serviced. The SX-1250 is not a good unit to probe around without some prior experience. If you have a rudimentary background in electronics we can probably walk you through the checks and analysis.
 
Watthour said:
Welcome Aboard!

If the speakers are at least 8Ω or are used only one pair at a time the unit should be able to power them unless there is a wiring problem or damage to the speakers/crossovers. Speaker resistance can be checked with your ohmmeter when disconnected from the unit. 8Ω impedance speakers will typically exhibit at least 6Ω DC resistance. Lower than that might indicate problems.

Presuming the speakers are verified intact, there are several things which can be checked and potentially a few adjustments which can be made. DC offset of the output amplifier stages can be checked and adjusted. Quiescent or idle current of the final output drivers can be checked and adjusted if necessary.

However, before any of that happens it will be necessary to obtain a copy of the service manual and diagrams. The layout, schematic details, and procedures are all described in the manual. Before checking the offset and idle current the power supply voltages need to be checked. This requires measuring voltages in the unit in some rather congested locations. Caution must be exercised to prevent personal injury and/or damage to the unit. Voltmeter probes should be insulated all the way to the tips to prevent inadvertent shorting. If opening the unit and performing several measurements is not an option the unit should be professionally serviced. The SX-1250 is not a good unit to probe around without some prior experience. If you have a rudimentary background in electronics we can probably walk you through the checks and analysis.
Click to expand...
Wow, I'm floored by all the data.... Can't wait to get stared but will be awhile yet... Having to go out of country on business for a while but when I return, this will be high on my to do list.. However. I reading on a different post earlier about running two speakers on "A" and two speakers on "B" at the same time
(all 8 Ohm) may not be good to do at one half volume and above ? I have a SA-9900 and SA- 9500 , should I run two speakers on each whilst jacked together from rec out on SX-1250 yo AUX on SA-9500 ? Eventually I want to run three sets of 8ohm JBL (4X L-112's) and (2X L-166's, How would connect the SX to the SA and which one would do best with 4 speakers connected? This all will be played in a high volume regime ?
Thanks,
PS Love this Forum already !!
 
I agree with "watthour" above. My first thought was also speaker impedance. Check them as "watthour" says above and run only one set at a time. Without more info it appears that the protection circuit is doing it's job, a good thing! Bob
 
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