| pjaneiro |
I finnally fixed my carver brick, i love this amp, ever since i sold my old 1200 i was sad all the time, i finnaly got my hands on a 1.5 wich is actually the same thing....well i think, i remember my 1200 having 1.5a boards in it, Anyways my problem is quite simple, on my 1200 i had gotten rid of the power down sound it made with an "upgraded" board i had gotten from a service center, and also they had sent me a service bulletin with pics on how to upgrade my inoput board for the output noise in the left channel, well the 1.5 is now fonctionnal but i have no idea where to get that upgraded board for the power down noise, and my input board has no marks identify the jumpers numbers so i can upgrade my input board...anyone has an idea, i know there a few carver gurus around here...
P.S. is there a way to change the motor driven fan to a dc fan ? |
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| pjaneiro |
| No one heres knows what i'm talking about ? I'm sure Anatech has some input....Where are you oh great one :D |
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| Netlist |
He's still drinking his morning coffee.
/Hugo :) |
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| pjaneiro |
| Come on guys, i'm going nuts over this one, for sure someone here knows what i'm talking about... |
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| anatech |
Hi pjaneiro, Hugo,
Sorry. Really slow out of the gate today. I'm not firing on all eight yet either.
Upgraded boards for a 1.5? Never seen one, but their was a circuit change (mod) available for excessive pops I think. It's entirely possible that a shop was doing the mods themselves. I believe there may have been "flying" parts involved (not mounted on PCB). I'll have a look in the archives.
Your fan is on it's own circuit. It is designed to vary the speed with the music. If you want to change it, you must use a slow run speed at the minimum, and vary the fan speed with heatsink temperature closely. Therefore you will need to sense the heatsink (chassis) temperature and your fan will be continuously variable. Your maximum CFM must be at least equalt to what you are taking out. The sensor needs to be shielded from the airflow.
-Chris |
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| pjaneiro |
Thanks for the reply, i was feeling all alone here... :xeye:
Hmmm for the fan speed, well this model does NOT follow the music, neither did my pm-1200 both are the disco models, both models have a switch for full or half speed, i'd be glad to send the service manual for your viewing,
well i dunno what shop was doing those boards but i do know i delt directly with a guy from carver pro, his email addy no longer works, the screetch sound at power down i could live with, but that also is "feature" that i'd love to get rid of but it's the output noise in the left channel that's bugging me, i have the service bulletin to correct this, but my input board has NO markings whatsoever, and in my service manual the markings are just unreadable (poor scan i guess) |
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| Tarzan |
Hold on, I have to look in my docs.
There is something written about upgrades.
I'll be back later today or tomorrow.
Cheers, |
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| anatech |
Hi pjaneiro,
Ah, Carver Pro. They were not connected with the Carver service network at all. I did a repair for them and they didn't pay me, so I wrote them off. They may have figured something out. I am still looking through the mods.
In the back of the manual, they would list all factory changes to date. Still, I have some more info somewhere.
What this sounds like is the LV power supply is dying before the main supplies. There was one mod were they added resistors to drain the main supplies faster. I didn't like doing it because it generated more heat and would cause other problems down the road.
If you could, could you send the manual to bhomester at gmail dot com? I'll have a good look. They may have adapted an earlier mod to this later amplifier.
-Chris |
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| pjaneiro |
| Thanks i just sent it, also i've read in one of your posts that an easy way to transform a regular line out to a balanced line out is to use a ssm2142, i've looked around but can't seem to find a schematic for the use, anyone can point me to the right direction ? |
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| pjaneiro |
| Anatech, do you have otehr mods for this amp ? i only have the output noise in left channel mod and the power supply capacitor board bulletin, if you have any other info it would be appreciated... |
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| pjaneiro |
Hi tarzan, did you have any luck on those upgrades notes ?
Thanks... |
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| anatech |
Hi pjaneiro,
I still have another box to dig out. I believe there were a few changes. The rule was, don't change something unless there was a need to!
The new current part for the SSM2142 is the DRV134. It's the same thing with improved specs. Don't go balanced unless you need to solve a problem, otherwise you just end up with more parts in the signal path. More distortion.
You always have to "balance" one problem for another. You go with the least problematic solution. This means that if you don't have excessive noise pickup, stay with single ended! Your equipment is ultimately single ended inside, so you are just sticking adapters on each end. The adapter is built in the Carver, but it's still outside the single ended chain.
I got the schematic - thank you.
-Chris |
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| pjaneiro |
Hi all,
I still can't seem to find that info for the output screech..danm... |
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| Tarzan |
So it took some time, family matters...
I have the schematic of the 1.5 with some service notes.
valid for serial numbers:
before 20850, Service Bulletin (SB) 5A-2:
Driving the output stage level tp a maximum witout a load...
before 22600, SB 5A-3A:
Mounting the output trans reversed...
before 21176, SB 5A-1:
Second fan running slow...
as needed, SB 5A-4:
Truly balanced input stage...
That's all I have...
All other info is welcomr to this way...
(even for the PM-1200 or other Carvers)
CHeers,
Tarzan |
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| anatech |
Hi pjaneiro,
There are no changes for that listed for the PM 1.5 or 1.5a. The M-4.0t has a mod for turn of thump. The TFM 45 has a mod for turn off squeel. It may be in the back of the manual, I don't seem to have it.
Before you do anything. Does your unit have two blue dual section caps on the power supply board, or a circuit board with four capacitors on it near the middle, bottom (where the bottom bends up and straightens out again)? If it has the two blue caps, you need to replace that with the mod board. Some guys have installed the four caps without a board. These will cause all kinds of trouble.
-Chris |
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| pjaneiro |
I have modded the amp with the new 4 caps, actually replaced them with higher voltages and capacitance values, just to be on the safe side, this unit is actually driving 4 15" subs at a rated power of 400w, when this baby goes on my chest want to implode and the party goers go crazy !!!!
but that damn squeel at power off drives me nuts, and that left channel noise also, i got m hands on part 2 of the service bulletin for the carver input board, that carver company liked to keep their secrets, once again, no info on wich jumper is wich...., i could take a guess and just cut the ones on the left channel but hey, i dont feel like turning on the amp and getting a nice 600w humm blowing the speakers away, ;)
i can take pics of the input board if any of you gents feel it might be needed |
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| anatech |
Hi pjaneiro,
Let's look at the TFM-45 shematic and figure out if the mod is backwards compatible. Could be the added capacitance is the problem by keeping the amp running longer.
-Chris |
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| anatech |
Hi pjaneiro,
Okay, for the TFM-45 we have to watch the brand of op amp. See the following, it's mentioned but not the main object of the bulletin. |
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| anatech |
Hi pjaneiro,
This mod addresses your problem directly as it applies to the TFM-45. It's meant to discharge the supply more quickly, so you may have caused this by increasing your capacitor size.
I would replace those with the proper value as this mod will directly heat the capacitor terminals. You don't want to do that.
-Chris |
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| ApD |
Hi pjaneiro,
a couple of ideas from me:
1. The squeal is definitely coming from the OP-amps on the input ckt. Bob Carver said in an interview that he always adds pull-up resistors from op-amp outputs to LV(+) to force them into SE class-A operation, which should also fix the squeal issue - check whether they are there. If not, 10mA should do the trick.
If that does not solve the problem:
2. Why don't you run the audio signal output from the input pcb to the main amps inputs through a 5V reed-relay, fed by the LV via a resistor and a (sufficient) cap in parallel to the relay coil? This way the relay will switch on/off only after the LV is high enough, leaving some time for the OP-amps to settle, and will switch off before they die into a squeal.
Best, |
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| anatech |
Hi ApD,
Don't use pull up resistors.
I do not recommend modifying the input circuit. This is not a design fault. If Bob intended to use pull up or down resistors, he would have installed them.
The engineer who approved these mods was Vic Richardson. I used to talk to him often. These changes are the ones to use, Vic has the ability to solve these problems properly, and he did. I've learned to respect his judgement over the years.
-Chris |
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| ApD |
Pull-ups do no harm. They help sometimes.
Offtopic:
If these gyus are as good and thorough as you say, I wander where they were during the design phase of the amp - why did they let it out of the factory door in such a condition the first place... I wouldn't. :) |
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| anatech |
Hi ApD,
There is evidence that forcing op amps into class A may not always help. In any event, you shouldn't give this a blanket recommendation. If you wanted to do this, a current source would be much more linear. Look at the Marantz 3600 / 3800 preamp for an example (uA749 or 739, can't remember).
| quote: | | If these gyus are as good and thorough as you say, I wander where they were during the design phase of the amp |
There is more than one engineer on staff, each are assigned a project. Cost cutting accountants force creativity against most engineer's best judgment. Service bulletins are the result. They may also make the odd error, but not often. Given that we don't belong to a perfect world, you can expect these things.
If you want to see bad designers, there are many products that will fit the bill. A long list. Once you compare the designs you can appreciate the good ones. Look at the list of simple, stupid mistakes in basic circuits, then consider a system as complicated as, say a Carver amplifier. I'd say they have done a pretty good job.
I don't want to name names here, but I have seen many amps that cause fires due to poor design. Most are out of business - thank goodness!
-Chris |
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| pjaneiro |
Hi all,
The squeel was there even before i replaced the caps, it's a "feature" from carver, as my old pm-1200 had also, what i do now to remove the squeel is that turn dow the volumes on the amp,but now when i turn it off i hear the music still being played from my mixer going down and with distorsion, for the input board mods for the noise i still can't figure out what jumper i need to cut, they are not marked anywhere.... |
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| anatech |
Hi pjaneiro,
I haven't a clue what trace you are talking about cutting. There is no mention in any of my 1200 notes, or PM 1.5a notes.
May I see the document you are looking at?
Did you read the two service notes I posted? The number 2 document covers the squeel as it may exist in stock units, so it may apply to you directly.
-Chris |
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| pjaneiro |
Hi Anatech, in the service manual i sent you, page 1 of 2 is page 81 in the pdf manual and page 2 of 2 is page 21 in the pdf doc, it's all explained there on how to remove the output noise, but there is no clear indication on wich jumper is wich..
Thanks... |
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| Tarzan |
Hi pjaneiro,
If possible could you mail me the manual you have?
That would be great.
Here is my address:
dome
at => @
advalvas.
be
Thanks,
Tarzan |
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| pjaneiro |
| the adress you gave me is not recognized, send me a mail at pjaneiro >at< hotmail >dot< com |
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| anatech |
Hi pjaneiro,
That mod was for noise pickup from the mag coil. Kinda "tick tick tick" noise. You are running the signal via a twisted pair rather than the traces on the circuit board. The two jumper are simply the other end of the traces you are cutting. Follow the trace on the PCB.
You can do this if you want, I do not believe it will help you in the least unless you are also getting interference from the mag coil circuits. Nothing you have posted would lead me to believe this.
-Chris |
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| pjaneiro |
| the noise is more of a high pitch buzzing from the left channel my pm-1200 used to do it before i did the mod, ok i'll follow the traces and see where it leads me , thanks |
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| anatech |
Hi pjaneiro,
That will help the high pitched buzz. I think you'll find the mod fairly straight forward.
-Chris |
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| Bonsai |
| Does anyhone have a circuit diagram for this amp. If so, could you post it or email it? |
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| pjaneiro |
| i have the service manual, but it's 10mb, i've tried to send to a few people but their email account bounced back, i would need a site where i could upload it |
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| anatech |
Hi pjaneiro,
Did you try the mod yet, or are you waiting for the weekend? It should take you 1/2 hour or less to do this.
-Chris |
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| docfin |
pjaneiro ,
could you send it to me?
my mailbox unlimited, docfin @ gmail . com (remove spaces)
thanks in advance
John |
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| anatech |
Hi John,
You should have mail very soon ....
-Chris |
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| pjaneiro |
| I should have some time tonight to try this one out, for the other mod abot the squeel, no go, i do not have the same boards, so i won't venture myself into that one, i was wondering if i could just use relays to cut the output stage to the amp ? that should work no ?, as i stated i only hear the squeel when my mixer is on with music still playing |
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| anatech |
Hi pjaneiro,
That will work of course, but defeats the normally quiet design and effectively protected Carver amp. You will need the really big ones. You may have trouble with contacts due to the high peak currents this amp will deliver.
Why not use a signal relay to short the input when you switch off?
-Chris |
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| pjaneiro |
| mod worked perfectly fout the high pitch buzzing, i noticed something , the ground post for my speakers has a wire soldered going to a 2 screw post connected to the chassis, but this wire has been cut, and the wire connecting the 2 screws are removed the amp works fine, but should i solder back the ground to the chassis ? and put reconnect that 2 screw post ? |
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| anatech |
Hi pjaneiro,
I think your are referring to to the barrier strip with two screws on the back of the amplifier. Chassis ground goes to one terminal, circuit ground to the other. There should be a shorting strip between the screws on the back that you can removeif you want to float the circuit ground.
It made no sense for anyone to remove those wires.
-Chris |
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| pjaneiro |
That's just it, i do have the barrier strip istalled, but internally the ground wire going from the barrier strip to the ground speaker wire has been cut, and to my dismay i just soldered it back, POOF ! my ground path in the output board of my mixer is now vaporized, what the hell ? could it be that the previous owner cut that ground wire because of a problem ? or is there a ground difference between the power amp and home appliances ? they both use grounded pin wires !
Thanks... |
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| anatech |
Oh Man!,
There is something seriously wrong there!
The chassis ground should be at the same potential as everything else unless your house wiring is bad. It's now time to examine everything carefully and assume nothing. That means check your outlet wiring and the internal wiring. Unplug and measure the resistance to the line cord from ground, both sides. I wonder if a transformer leak / short to core has occured. The amplifier would then be unsafe to sell.
I'm glad you didn't get a shock or worse!
-Chris |
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| pjaneiro |
well i checked the amp, i see no short, but i did notice one thing, i remember a while back that i needed to have a ground lift for some of my items when i used my pm1200 also, i remember that when i plugged my laptop to the amp or even to my house amp (el cheapo yamaha) i would get the famous 60hz hum even the image on my tv would get the 60hz roll, could it be the same issue for my mixer ? btw i had an old laptop lying around i connected it direct to the carver running on batt worked fine, as soon as i plugged on the 3 pron batt charger, the poor sucker died right there, same phenomena the ground path connecting to the 1/8 jack totally burnt off, there goes a good old toshiba 386 !!!, so i think i'll just put the amp back as it was, i've talked to a few of my friends who also dj's and they told me that they have a lot of issues with the power amps they use concerning grounds, they have mismatches of crown's, qsc's, bgw's and they told me horror stories of some amps still having the chassis to output barrier still on and having fire coming out of the torro coils as soon as they plugged them in on the same mixer, funny how household technology and disco don't quite work the same....or am i just talking non sense ?, if it were'nt true why would the enginers put those lifts there in the first place ? Please correct me if i am wrong...I checked my mains in the house, i just get a steady 244 ac when i connect my tester to the hot wire and the ground !!!!!!!
JUST KIDDING...... |
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| anatech |
Hi pjaneiro,
The ground lift is for reducing the level of hum, not for preventing sparks and smoke.
You must have a serious wiring fault in your home AC electrical outlets.
Buy an outlet tester. Test each and every outlet that you use. I am worried about open grounds and / or hot and common mixed up. The other possibility is that your mag coil is shorted to the frame and chassis. Either way, there is no way that amount of current should ever flow between grounds. I don't think there is a member here that would disagree.
So don't cover the problem up, FIX IT!
The only difference between commercial and home wiring is the quality of the work. The outlets ought to be wired the same way.
-Chris |
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| pjaneiro |
Well i just did something better than that , i just installed myself a new braker and a new 3 pin wire to it, same results, i am also using a powerbar/noise suppressor from monster, all lights indicate clean power with good grounds, i've checked for a short in the amp all is good, excuse me for my ignorance but why is the negative prons on my amp connected to the chassis anyways ? i am still trying to figure out that one, i thought sound was sent in AC form ? i've just checked with my home amps (nad / yamaha and my good old trusty dynaco, nope no ground connected to chassis there....even for fun i checked my car amps, only one actually has a neg speaker post to chassis, and yes i checked the positive side also, as i know some car amps invert signal for bridge :-)
please enlighten me, i find this fascinating, Oh yeah, another stupidity, since i reconnected the neg speaker back to chassis, the squeel is gone !!! :xeye: |
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| solderhead |
| quote: | Originally posted by pjaneiro
P.S. is there a way to change the motor driven fan to a dc fan ? |
The PM-1.5 fan actually is a DC fan. The DC voltage supplied to the fan is increased as the load on the amplifier increases. If you try driving the amp into a dummy load, you'll hear the fan speed increase as the power demand on the amp in increased. |
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| anatech |
Hi pjaneiro,
Please use caps and punctuation properly. Your post is hard to read.
| quote: | | excuse me for my ignorance but why is the negative prons on my amp connected to the chassis anyways ? |
prons??
If you are referring to the AC ground pin, it's connected to the chassis for your safety. Should anything short to the chassis to make it live, the ground connection directs the current to the AC return rather than through your body. It's actually a law and a requirement for UL and CSA approval.
If you are talking about the black (or common) speaker connections, you will be able to measure continuity to the chassis ground. There is no speaker AB switch to interrupt that connection. The speaker return must not travel through the chassis or RCA ground.
| quote: | | and yes i checked the positive side also, as i know some car amps invert signal for bridge :-) |
The Carver M400 did that too. Other Carver amps did as well, but I can not remember which ones did that.
-Chris |
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| romani |
Would it be possible to get a copy of the service manual?
I've got one sitting on my test bench that needs some tlc... |
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| Inch-o |
Hi There,
I have a PM-1.5 sitting on my desk with that "hi pitch noise" coming from the outputs.
I did some checks on the MAG COIL regulator and could observe that the noise is related to the TRIAC switching.
I have only the schematics of the PS section.
Can anybody mail me the service manual or complete schematic?
Regards
Inch-o |
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