Got a hold of a (very clean) GP7SM130 combo (EDIT: I think this model might be the 715SM after further research) . It's the head with the 1x15 cab. The cab has two round ports with removable caps. Cant seem to find any literature on the Trace site to give me any kind of specifics on what these will do exactly if I remove one or both. Any help? PS. I got this combo in a trade and it may be for sale or trade in the near future if anybody is interested. Thanks EDIT: Now for sale, http://www.talkbass.com/forum/showthread.php?t=691711
The plugs/caps change the cab from ported to sealed. In ported mode it is louder but does not extend so low. Adding one plug cuts the output slightly but lowers the lower frequency resonse. Adding both reduces output further and lowers the lower frequency response further. I have the 1 X 15 combo with the same amp and graphic preamp but double the output power so you can run an extension cab. When I first got it I tried messing about with the tuning plugs and ended up leaving them out (and loosing them). If I can dig out the manual I will post the specs on them. As a side note. There is an inherent design fault in the amplifier section. There is a missing star washer where the power amp earth is connected to the chassis. Without this there is a distinct possibility that it will self destruct or self combust as mine did. As far as I recall the chassis connection is at the front left corner of the power amp. Remove the screw and check that a star washer is fitted. If not fit one. Most old ones have self destructed and been replaced with the more modern mosfet replacement. I have a pdf of the complete service manual if you want to PM me.
Wonders will never cease. I have found my original user manual and receipt, not bad considering that I bought it in 1997. Both ports plugged = Infinite baffle One port plugged = Reflex enclosure tuned to 35Hz Both ports open = Reflex enclosure tuned to 45Hz
OK, took the amp head out of the cab. First of all, even though this amp has been stored for quite a while, basically unused (I got it from a drummer that "tried" smug to play bass at some point), I've got to give it up for (the former version of) Trace Elliot. The amp didn't even get dusty inside! And this is Las Vegas. Everything gets dusty here. The wiring is all very clean also. Nice. Now, there are no ground wires of any kind coming off the power amp section. The only grounding wires are two: One coming from the power receptical jack and the other from the ground lift switch that both terminate at the same circular screw tag end on the bottom of the chassis near the power transformer (rear right inside the amp). Although there is some kind of small washer between the nut and the circular screw tag, I don't know if it's a star washer as the circular screw tag is making fine contact with the chassis. (BTW, the inside of the chassis is scored under the screw tag to make sure of good contact. Go, Trace Elliot!) I'm no electronics expert, but my knowledge is more than mere basic and I'm a little confused as to where and what difference this star washer would make to the amp, other than to hold a nut in place. Anyone know what this concern might be?
That is where the star washer should be, between the tag on the end of the wire and the chassis. It can be fine for years but get a little bit of corrosion in there and the whole thing goes unstable, starts making random frying bacon sort of sounds and eventually takes the power amp out. Mine then took the speaker as well. TE recognise this and it an official mod to add a star washer. Mine is a 7215SM, 7 for 7 band graphic, no idea what the 2 means but probably for it's 2 preset bass shapes , and 15 for 15" speaker, SM is for Sound Mangement. I bought it new in 1997 and apart from the little episode with the star washer has been a superb amp (combo). I fitted the later mosfet power stage and an Eminence Delta speaker, plus a couple of piezo horns because the Delta's top end range was a fair bit down on the original Celestion. The first thing I did with mine was fit a set of wheels on it and get a cover. It looks almost new and has done hundreds of gigs. If you are keeping it then it is not a bad idea to blow the dust out of the heatsink and fan every few months.
Weird. I would think the flat connection would contact better. Plus, with no dust after all these years I can't imagine corrosion getting in there. Oh well, I'll just put a star washer on it. Did your combo look like this? The head is 130 RMS/260 Peak (GP7SM 130). I've had info on this model come up as 715SM several times. No "2" in there, but you can see it has the two shapes plus all the other bells and whistles. {} {} {} {} {} {} {} As you can see, very clean for it's age. I'm so into the MarkBass stuff now, I'm debating whether to sell/trade it or keep it. It's a bit more than I need for a practice amp.
The star washer digs into the metal on the chassis and tag resulting in a lot higher pressure over a smaller area. This higher pressure means any moisture is less likely to get in and cause corrosion. Maybe where you are there is not that much condensation, but if I take my amp out of a cold car or van into a hot humid club and set the fan going it gets condensation inside it in seconds. Not only did my combo look very much like that but it still does, I gig with it regularly. Mine is 280W RMS total. I never use peak as the only real measure of power is RMS. Nowhere on the combo does it give the model number but the receipt and the registration details list it as 7215SM. It is slightly different to yours, I suspect yours is a newer model with slightly different graphics. Also mine is 280W as opposed to your 130W. Maybe the 2 means it will run an extension cab as well. Only once have I done this as it is usually quite loud enough. I ran an 8 ohm Peavey 4 X 10 and it sounded really good. I am still looking on old disks for the manual, will send when I find it. It is very clean for it's age, mine is fairly clean but it has seen a lot of action so is bound to have deteriorated after 13 years of regular gigging. I do periodically blow it out with an airline and give the rat fur a good clean with a Hoover. What looks the worst is when dust settles in the ports.
The RMS/Peak thing is how it reads on the back. The model and serial were written in spaces on the back, but have mostly rubbed off. I can, however, somewhat make out the model and it does look like it probably says 715SM. On yours I suspect the "2" is for the number of speaker outs. From what I've researched the higher wattage versions of these seem to have dual outputs for an extension cab. Mine only has the one 4 ohm out for the internal 15. FWIW, I've owned many 120-150 watt (rated) amps. This seems to have a lot more power at a 130 watt rating than those did. I've only used it in my house so far, but I haven't made it fart yet. I am in a host band that does an open jam gig every Wednesday. I'll take it this week with my regular rig and give it a go. I'll report back for anyone who is interested. I live in Las Vegas...the desert. I probably won't ever have a corrosion issue, but I'm going to put a star washer in there anyway in case I sell it and it finds a new home in a different climate. Thanks for all the help.
doohh, never thought of that. Manuals are on their way, user and service. I am interested in what you think of it.
Got 'em. Thanks. I threw it up for sale locally (Craig's List), but if I still have it by Wednesday I'll do a gig report (I'm kind of afraid I'll like it and have to keep it ) .
UPDATE: Went in to deal with the star washer thing and it turns out there's one already on there, but it's between the nut and the tag end, not the tag end and the chassis. It's obviously there to keep the nut from loosening (which might have been the actual real problem for you and other users as well if that star washer was ever omitted). So, after consulting the Dept. of Redundancy Dept., I added two more star washers. One in the original spot of issue, between the tag end and chassis. And another on the outside between the screw's head and the chassis. Short of somebody throwing this thing in the ocean, there will never be a question of a secure ground at that point of contact. Now up for sale kiddies: http://www.talkbass.com/forum/showthread.php?t=691711
I don't think you, or the new owner, are ever going to have a problem with a bad earth connection now but you may have to update the spec weight to include all these star washers.
Phat and delta7, Think I could get a copy of those manuals since I am the proud new owner of Phat's trace combo thanks, Brian
I never had a manual. All the info I have is here from delta, or browsing Trace-Elliot.com by way of Peavey's site.
Brian Sorry for the delay, I have been away for a week. Is it the full service manual, or just the user manual? If you want the full service manual PM me and I will send it. or if you are a member of freestompboxes.org then it is here http://www.freestompboxes.org/download/file.php?id=7186 fred
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