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Post by paradisecs on Apr 2, 2018 15:18:22 GMT
I have a SHP3 amp that is missing the GMQ fuse so I thought I'd try one from another amp to get it up and running. It didn't physically fit (to long of a fuse). I pried the fuse out and put in a shorter one and the cap does not fit. Upon inspection the socket has been replaced from the original factory version and I can not find a cap that fits the one I have. I'm going to just replace it but is there a particular type or brand anyone would recommend or will any panel type holder work?
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Post by Ron Rich on Apr 2, 2018 16:37:23 GMT
gottem partz manual--look at it--SHP-3's don't use a GMQ fuze ! A "normal" panel mount fuse was used there. Ron Rich
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Post by robnyc on Apr 2, 2018 20:04:15 GMT
gottem partz manual--look at it--SHP-3's don't use a GMQ fuze ! A "normal" panel mount fuse was used there. Ron Rich -To which I'll add; do not go above 2amp/slow (I use 1-1/2-slow). RobNYC |
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Post by paradisecs on Apr 2, 2018 21:17:34 GMT
GMQ or not I need to replace the holder. Thanks for the info on the 1.5amp fuse, I was just going to replace with 3.2 as directed in service manual.
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Post by Ron Rich on Apr 2, 2018 22:33:41 GMT
To be honest--the first SHP-1's came with a 1.6 GMQ fuse. It would blow for "no reason", so they increased it to 3.2, where if everything's OK, it would be fine--but if something does happen, that 3.2 will NOT always blow in time to save the transformer ! I suggest that 1.5 is too low, I use 2.0 amp (GMQ's, if that the type socket installed) Slo Blow's--Ron Rich
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Post by paradisecs on Apr 2, 2018 23:56:35 GMT
Why are slow blow or time delayed used instead of standard ones?
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Post by robnyc on Apr 3, 2018 1:36:37 GMT
The reason for time delay is to allow for sudden surges such as capacitor inrush at turn-on or other transients without nuisance blowing.
The originally spec'd 3.2 was bizarrely over-rated. As Ron points out, it allowed for a lot of damage before it acted to "protect" anything. These amps were woefully under-fused and this just made it worse. It is why nearly all of these have scorched driver boards and often burned out traces.
In reality this is a 35w/ch amp. Under normal use it rarely exceeds 1 amp on peaks even fully loaded.
Ron recommends replacing the AGC "stabistor" diodes and I agree. Not only does this improve AGC leveling, but it keeps the amp's gain structure within the design limits and helps prevent excessive current on loud records.
RobNYC
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Post by paradisecs on Apr 3, 2018 23:05:06 GMT
I got lucky and found a cap that would fit the socket on the amp while sifting threw my boxes of arcade parts. I put in the 1.5amp slow blow and now I have power to the amp but I'm only getting sound from the needle, not the amp/speakers. The SHP3 was recapped in the past (not by me) and was pulled from a working unit (or so I was lead to believe). I can make selections just fine and the record plays through and then moves on to the next selection with no trouble, just no sound. I'm travelling today but I will get back to my books and guides later this week. Is there a problem in the network junction perhaps?
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Post by Ron Rich on Apr 3, 2018 23:44:50 GMT
All the plugs plugged in--correctly--volume up ?? Ron Rich
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Post by paradisecs on Apr 4, 2018 2:38:17 GMT
So far I haven't found anything not plugged in and yes the volume is up, checked that first. If I take my phone and plug it in to the rca input jacks on the amp will that cause any problems? My thinking is if that works then it is the wiring coming to the amp and not the amp itself. Not sure what else it could be yet but that would rule out one possibility. I also have a working STD160 sitting next to the the SPS160 that is having the issue. I can swap the SHPs and see what happens, I just worry if there is a greater problem if it will mess up the known good amp. I'm going over the SHP amp guide, slowly.
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Post by robnyc on Apr 4, 2018 13:02:06 GMT
It is unlikely your phone will work because of the odd way Seeburg designed the input. Ir requires approx 400-700 ohms across the input to properly bias and turn on the first transistor in the preamp. A simple "L" pad can be built using an approx 560 ohm resistor across the input and around 100k-ohms in series with the source. In this example: www.electronics-tutorials.ws/attenuators/l-pad-attenuator.html R1 is the 100K-ohm and R2 is the 560 ohm (or reasonably close). This will be a bit too bassy due to the equalization intended for records -but you will get sound. What tools do you have? A simple digital multimeter that can read AC down to the millivolt region will tell you if there is signal at the RCA plugs from the pickup playing a record. Try plugging in a turntable with magnetic pickup and put mech in play. What is the result? Connect an external speaker(s)to the amp outputs. Let us know what you find. RobNYC |
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Post by Ron Rich on Apr 4, 2018 14:02:52 GMT
Swapping amps will not hurt the good one ! Ron Rich
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Post by paradisecs on Apr 5, 2018 3:11:33 GMT
Thanks for the info. Swapped the amps around and sure enough, the SPS started working. Put the questionable amp in the known working STD and same thing, no sound. Now I get to troubleshoot my first amp. All the caps have been replaced in the past but I have no idea when.
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