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SANSUI AU-719 Gets Really Hot?

I recently acquired a Sansui AU-719 which gets extremely hot. I have other Sansui's (AU-417, AU-517, AU-717, AU-7700, Etc.) and though they do get warm, none of them get anywhere near as hot as the AU-719. I listened to it for about 6 or 7 hours the other day (I only listen to vinyl) and as happens from time to time, after a few beer, the volume tends to go up:) Still never exceeded half volume and it was more than loud enough (think the neighbours hate me now), yet it got extremely hot, so hot in fact, that I could not keep a finger on it for more than a second or two for fear of actually getting burned. If this is normal for this model then I can hook up a small fan near it to help dissipate the heat. Today I've had it on for about 2 hours at just less than 1/4 volume and it is a bit warm but by far not too hot. I tried researching this on line and found two opposing points of view, some said it is normal while others said that the excessive heat probably indicates a problem which if it not fixed, could fry the amp. Any input would be much appreciated, thanks;
Denny
recordman34
stanwal's avatar
stanwal
3,147 posts
 
I checked with a 1979 isssue of HI -Fi Choice. The 719 was not tested but the 417 would produce 80 watts at 8 ohms tested driving one channel only it was 100/150/171 at 8/4/2 ohms. Burst power was 130/211/300. For the 919 the numbers were 145/210/275 and burst power 164/314/543. The 719 should be between these closer to the 919 than the 417. Burst power is a measure of short term capability that is relevant to performance on music which generaly does not call for constant full power. These numbers make me think that yours is not working properly.
rrog
1,958 posts
 
Specs for Sansui SP-7500X are as follows:

16" woofer; 6 ohms
8" midrange; 8 ohms
6"x2" horn; 8 ohms
2" tweeter; 8 ohms
rrog
1,958 posts
 
Stanwal, Please explain. I don't understand how the numbers you posted make you think the OPs amp is not working properly.

I think the easiest test would be disconnecting the second set of speakers and only running the Sansui SP-7500X, the speakers the AU-719 was designed for. This would be much easier than having the amp checked by a tech. The OP also mentioned in his post playing music at half volume which I assume is the 12 o'clock setting on the volume control. This setting could easily be approaching the amplifier's limit.

Although the model numbers are similar the amplifiers can be quite different on the inside and I believe the AU-719 was designed different than previous models.
rleff
1,065 posts
 
I would suspect filter caps that have dried up some and are becoming resistive producing heat as well as output transistors that maybe seeing a higher bias than they should be and heating as well.
recordman34 OP
7 posts
 
Thanks again, I'm going to try to get someone to look at it as I discovered another problem last night. The Tone Defeat switch works just fine in the "Defeat" position" but in the "On" position the right side cut out on me (although it had been working just fine in the "On" position up til then). I cleaned it prior to hooking the amp up last week. I tried it again this morning and once again the right side cut out so I moved the switch up and down quite a few times and sometimes all four speakers would work, sometimes just one side would work and a couple of times neither side would work (while in the "On" position / all four speakers seem to always work in the "Defeat" position though). I don't think that has anything to do with the excessive heat but as I'm finding out, this unit has some issues. Later today I'm going to try it with just two speakers and see if that makes a difference with the overheating issue, then I guess I'll just have to hook up one of the other ones for a while and see about getting this one fixed, Thanks again for all the help, I really appreciate it because if you haven't already noticed, I'm not exactly technically inclined when it comes to these things:)
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