petetexas Posted January 31 Share Posted January 31 (edited) Hi , I just got hold of an old Peavey T Max Head , when its running its quiet but when I switch it on or off , there is a loud pop through the speakers .( Its an old Solid State amp ) The way I get over it is to connect the speakers after switch on . Anyone any suggestions ? Pete Edited January 31 by petetexas Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted January 31 Share Posted January 31 Leaky DC blocking caps on the outputs? 1 Quote Link to comment Share on other sites More sharing options...
itu Posted January 31 Share Posted January 31 Vol to 0, when turning ON/OFF. Quote Link to comment Share on other sites More sharing options...
Pea Turgh Posted January 31 Share Posted January 31 I wouldn’t disconnect the speaker to switch on & off - that might cause damage. Pretty sure Eden stuff is labelled to that effect. 2 Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted February 1 Share Posted February 1 (edited) Yeah, don't have the speaker disconnected while the amp is turned on, the output transformer won't like it, and you could potentially risk ruining the amp. Edited February 1 by Baloney Balderdash Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 1 Author Share Posted February 1 Volume on zero ( main and pre amps ) graphic switched out . When switching it on / off at the mains , the pop is quieter . I was always told that with Solid State Power amps , no speaker connected is the same as having an infinate resistance ? I`ll get in touch with Peavey and see what they say . Thanks guys Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 1 Share Posted February 1 3 hours ago, petetexas said: Volume on zero ( main and pre amps ) graphic switched out . When switching it on / off at the mains , the pop is quieter . I was always told that with Solid State Power amps , no speaker connected is the same as having an infinate resistance ? I`ll get in touch with Peavey and see what they say . Thanks guys hi, if the amp is oldish then it could be that any anti-pop components fitted have aged, or as mentioned above, a DC blocking cap at the output has become leaky, and affected parts might now need replacing If this is not the case, and there are any concerns about switching on the amp minus the speaker, then another approach could be to make up a small external load box, containing a resistor of say 100-200 ohms and 5-10 watts rating. Have this plug in to the amp output socket before switch on, and have an extra socket on this box to then plug in the speaker after switch on, disconnecting the fixed load resistor ...just an idea... Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 1 Author Share Posted February 1 sandy_r ☺️.........Brilliant idea........thanks........will wait to see what Peavey say, but if they take too long , I will build one......... thats brilliant . Thanks 1 Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 1 Author Share Posted February 1 A guy at Peavey has got back to me , and suggests that I get in touch with the service / repair guys at Corby , and ask them about plugging in the speaker after switching on the amp . Rang Peavey at Corby , but the engineers are away at some show till next week . The guy on the phone did say that Solid State Power sections do not have an output transformer ( valve amps do ) I'll give them a ring next week . Confused now........ Pete 1 Quote Link to comment Share on other sites More sharing options...
itu Posted February 1 Share Posted February 1 Output X-former is needed with valves/tubes, because the tube section's output impedance (Z) is high compared to speaker's Z. The transformer changes (transforms) the tubes' output Z to suit speakers' Z. Solid state (transistor) power amp has low Z output, and the transformer is not needed. It is not a bad idea at all to have the load (cab) connected to the amp. 1 Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 9 Author Share Posted February 9 (edited) Peavey say they think it could be the mains on / off switch causing an arc during switching giving the pop through the speaker . Does anyone know what resistor and capacitor value I could use for soldering across the contacts in the switch , to stop the arc ? A couple of articles I have read are sayin as a rough guide ........ 1ohm per volt for the resistor and 1mf per amp for the capacitor across the contacts = 240ohm + 16mf . Anyone know ? Pete Edited February 9 by petetexas Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 9 Share Posted February 9 16 minutes ago, petetexas said: Peavey say they think it could be the mains on / off switch causing an arc during switching giving the pop through the speaker . Does anyone know what resistor and capacitor value I could use for soldering across the contacts in the switch , to stop the arc ? A couple of articles I have read are sayin as a rough guide ........ 1ohm per volt for the resistor and 1mf per amp for the capacitor across the contacts = 240ohm + 16mf . Anyone know ? Sheesh! ...are Peavey suggesting that this Amp has arced inside the Mains switch, at power on/off, for its whole life?!? Is this regarded by them as a design feature?!? Don't think it would have lasted a year of regular gigging & rehearsals! Something else has failed, to cause any such arcing (if it exists) - needs a Tech (with more dedication than Peavey) to inspect and fix Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted February 9 Share Posted February 9 42 minutes ago, sandy_r said: Sheesh! ...are Peavey suggesting that this Amp has arced inside the Mains switch, at power on/off, for its whole life?!? Is this regarded by them as a design feature?!? Don't think it would have lasted a year of regular gigging & rehearsals! Something else has failed, to cause any such arcing (if it exists) - needs a Tech (with more dedication than Peavey) to inspect and fix 100R and 0.1uF is pretty standard Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 9 Share Posted February 9 (edited) 3 hours ago, Bigguy2017 said: 100R and 0.1uF is pretty standard 'Snubbing' components are pretty standard - arcing isn't! Does the OP Amp have existing snubbing components fitted? Is arcing actually happening? Who knows? Somebody on the end of a phone at Peavey certainly doesn't! If it is happening (and only reliable tech inspection can advise), then WHY is it happening? Have some existing protection components failed? Is there a separate underlying cause? Just fitting/replacing 'standard ' parts may mask a more serious underlying issue - if the power on/off 'popping' ISN'T caused by arcing, then what is the cause? Get the Amp inspected by a reliable Tech and get an estimate for the work ...just my €0.02 Edited February 9 by sandy_r Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 9 Author Share Posted February 9 Is this the soft start board in the Peavey T Max. And is the other pic a capacitor . It only has two solder tags in the board, so it is not a relay . Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 9 Share Posted February 9 1 hour ago, petetexas said: Is this the soft start board in the Peavey T Max. And is the other pic a capacitor . It only has two solder tags in the board, so it is not a relay . This looks like a 1.5k ohm 15W resistor and a relay - i haven't found a resistor of this spec in the Amp schematic ...will keep looking for a bit What is your intention in using this information? Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 9 Author Share Posted February 9 The black square item , has only two tags connected to board , so it can't be a relay . Have you a schematic of the Peavey T Max then ? Pete Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted February 9 Share Posted February 9 58 minutes ago, petetexas said: The black square item , has only two tags connected to board , so it can't be a relay . Have you a schematic of the Peavey T Max then ? Pete Looks like a film capacitor ? Can't see the part numbers. There are a couple of pages in the manual showing this PCB with the 1K5 15W resistor, cap and fuse. Peavey-T-Max-Bass-Schematics.pdf Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 9 Share Posted February 9 (edited) 1 hour ago, petetexas said: The black square item , has only two tags connected to board , so it can't be a relay . Have you a schematic of the Peavey T Max then ? Yes, but the first didn't have the daughterboards - i've just found a different one which shows the board you posted above. That circuit looks like the dropper resistor and start capacitor for the fan, along with fuse and connections to thermal breaker I don't think that board is involved in softstart protection What is your intention in using this information? Edited February 9 by sandy_r Quote Link to comment Share on other sites More sharing options...
Dan Dare Posted February 9 Share Posted February 9 On 01/02/2024 at 07:00, Baloney Balderdash said: Yeah, don't have the speaker disconnected while the amp is turned on, the output transformer won't like it, and you could potentially risk ruining the amp. SS amps don't usually have output trannies. A very few hi-fi brands, such as McIntosh, do, but you shouldn't harm your Peavey by switching it on/powering it down without a speaker connected. Quote Link to comment Share on other sites More sharing options...
itu Posted February 9 Share Posted February 9 Could that be a VDR to prevent a current spike at the start? Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 9 Author Share Posted February 9 Thanks for the schematics Bigguy2017 Pete Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 10 Share Posted February 10 6 hours ago, Dan Dare said: SS amps don't usually have output trannies. A very few hi-fi brands, such as McIntosh, do, but you shouldn't harm your Peavey by switching it on/powering it down without a speaker connected. The harm can come plugging into the cab with a 1/4" lead and briefly shorting the amp across the tip and shaft, much the same as dragging your lead out of your instrument with the gain up puts one across the preamp. POP. Dead short plus solid state for too long is very bad business. 2 Quote Link to comment Share on other sites More sharing options...
Dan Dare Posted February 10 Share Posted February 10 4 hours ago, Downunderwonder said: The harm can come plugging into the cab with a 1/4" lead and briefly shorting the amp across the tip and shaft, much the same as dragging your lead out of your instrument with the gain up puts one across the preamp. POP. Dead short plus solid state for too long is very bad business. Good point. Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 10 Share Posted February 10 (edited) Under quiescent (no-signal) conditions, eg. following power-on with Master Vol at Min, there will only be a small fraction of a volt across the speaker terminals on such an amp (at the exact point where amp and speaker are designed to handle 10s of Volts and 10s of Amps) Normally** of no consequence to Amp or Speaker if the Speaker were to be plugged in at this time (and this is essentialy what many amps do internally with softstart protection relays) - as best-practice, I wouldn't do it, but YMMV [** on an amp within spec!] The OP has received a suggestion for handling the safe dissipation of the energy in this power-on/off Pop if he wishes to pursue this route However, all of the discussion so far is based on the symptoms of the OP issue - because noone (Peavey phone representative included) actually knows what is underlying cause of the noise - is it just a design flaw? - or is it the result of a failure in the amp circuitry, or in any existing softstart components fitted? Fixing a 'problem' mistakenly is 'very bad business' - much like putting a band-aid directly on an untreated, infected wound Amp-> Tech -> Inspection -> Estimate ...Just Do It! 😉 Edited February 10 by sandy_r Quote Link to comment Share on other sites More sharing options...
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