Hi.
One of the power trans, the softstart resistor and speaker relay burned when i would adjust the volume at the front pots. I replaced the parts and it tested ok.
But now it all burned again just by adjusting volume level at the front...
Is here anyone that knows what is going on.
BTW I dosn't have a diagram where I can locate the volume pots but I have the output section with power trans only. Where can I get a full diagram?
And it just burned again...
I replaced the burned output trans, soft start resistor and the speaker relay.
First 30 minutes without load and then 30 minutes of 2 Vrms in to 9.5 ohm dummyload was ok.
Then I decided to turn up the input signal, but with just a little more input signal, the same parts burned again, except for the speaker relay.
Any suggestions?
One of the power trans, the softstart resistor and speaker relay burned when i would adjust the volume at the front pots. I replaced the parts and it tested ok.
But now it all burned again just by adjusting volume level at the front...
Is here anyone that knows what is going on.
BTW I dosn't have a diagram where I can locate the volume pots but I have the output section with power trans only. Where can I get a full diagram?
And it just burned again...
I replaced the burned output trans, soft start resistor and the speaker relay.
First 30 minutes without load and then 30 minutes of 2 Vrms in to 9.5 ohm dummyload was ok.
Then I decided to turn up the input signal, but with just a little more input signal, the same parts burned again, except for the speaker relay.
Any suggestions?
eserviceinfo.com has four xls-602 schematics, including one only of the input board. You'll need an adobe pdf reader available from the IRS.
One possibility is that there is a bad solder joint that is causing a op amp input transistor etc to whang the output to the rail when the input goes up.
Or a bad capacitor is shorting out at the higher voltages.
You need to put the amp on a light bulb box to limit the damage when the fault occurs. This is a 100 W incandescent bulb in series with the AC power, in a grounded metal box with a AC socket, circuit breaker or fuse, and power plug. The box is to keep from shocking yourself if the wire pops off the socket screw terminal, as can happen with portable equipment. If the light goes on the amp is in failure state. I look in the back extra conduit hole of my box after I turn the AC power strip on.
Then take data with a DVM. Is the input to the VAS going out of control when you turn the volume up? That means the problem is before that. If not?
Or is there something about that one output transistor only? Is the insulation washer bad? Is there a burr on the heat sink?
If you're a newby, learn how to not kill yourself with the power on. Use only one hand at a time, voltage over 24 across your heart can stop it. Use a clip lead for the meter negative and put it on with the one hand. Wear no jewelry on hand, wrist, or neck. High current at 1 v can burn your flesh to charcoal. Test that rail voltage and input power voltage from the caps are down to < 1 v with the meter after the power is unplugged, before working on bad parts with two hands.
Best of luck.
One possibility is that there is a bad solder joint that is causing a op amp input transistor etc to whang the output to the rail when the input goes up.
Or a bad capacitor is shorting out at the higher voltages.
You need to put the amp on a light bulb box to limit the damage when the fault occurs. This is a 100 W incandescent bulb in series with the AC power, in a grounded metal box with a AC socket, circuit breaker or fuse, and power plug. The box is to keep from shocking yourself if the wire pops off the socket screw terminal, as can happen with portable equipment. If the light goes on the amp is in failure state. I look in the back extra conduit hole of my box after I turn the AC power strip on.
Then take data with a DVM. Is the input to the VAS going out of control when you turn the volume up? That means the problem is before that. If not?
Or is there something about that one output transistor only? Is the insulation washer bad? Is there a burr on the heat sink?
If you're a newby, learn how to not kill yourself with the power on. Use only one hand at a time, voltage over 24 across your heart can stop it. Use a clip lead for the meter negative and put it on with the one hand. Wear no jewelry on hand, wrist, or neck. High current at 1 v can burn your flesh to charcoal. Test that rail voltage and input power voltage from the caps are down to < 1 v with the meter after the power is unplugged, before working on bad parts with two hands.
Best of luck.
Hi.
Found the schematic, thank you for the hint.
Good ide idea using a 100 watt bulb to as protection. I do use a variable power source.
As I remember the output trans's is mounted without an insulator, and +- 95 volt is present at the heat sinks.
Next step is getting a bulb as protection and try again.
Found the schematic, thank you for the hint.
Good ide idea using a 100 watt bulb to as protection. I do use a variable power source.
As I remember the output trans's is mounted without an insulator, and +- 95 volt is present at the heat sinks.
Next step is getting a bulb as protection and try again.
Power Supply
The amplifier operates from nominal (off-load) +/- 65V (GB202), +/- 80V (GB402) or +/- 93V (GB602) supplies, with an auxiliary +/- 24V supply for the protection circuitry and the optional AMPSAP card. To generate the supplies, the mains transformer has one secondary with a centre tap, two 18Vac taps and the usual end taps. The end tap outputs are rectified by BR1 and smoothed by C1,C3,C5,C7 to get +HT and C2,C4,C6,C8 to get -HT (note: not all of C1-C8 are fitted on GB402 and GB202). The +/- 18Vac taps are rectified by D13-D16 and smoothed by C17 to get +24Vdc and C18 to get -24Vdc.
Soft Start System
AC mains enters the board on fastons (Red, Black, Blue) and leaves for the transformer by way of connectors Main1 (220/240) and Main2 (110/120). The soft start components are on the NEUTRAL line and comprise R22, PTC1, PTC2 and the contacts of RLY1. At switch on, R22 limits surge current and PTC1, PTC2 protect R22 from overheating. After a few seconds, the protection circuit energizes RLY1 coil, closing RLY1 contacts which short out R22, PTC1, PTC2, allowing full power operation.
The amplifier should be muted until RLY1 pulls in.
It won't work with the 100W bulb in circuit as there won't be enough current available when required at power up.
Why did you replace the speaker relay and which transistor did you replace?
The amplifier operates from nominal (off-load) +/- 65V (GB202), +/- 80V (GB402) or +/- 93V (GB602) supplies, with an auxiliary +/- 24V supply for the protection circuitry and the optional AMPSAP card. To generate the supplies, the mains transformer has one secondary with a centre tap, two 18Vac taps and the usual end taps. The end tap outputs are rectified by BR1 and smoothed by C1,C3,C5,C7 to get +HT and C2,C4,C6,C8 to get -HT (note: not all of C1-C8 are fitted on GB402 and GB202). The +/- 18Vac taps are rectified by D13-D16 and smoothed by C17 to get +24Vdc and C18 to get -24Vdc.
Soft Start System
AC mains enters the board on fastons (Red, Black, Blue) and leaves for the transformer by way of connectors Main1 (220/240) and Main2 (110/120). The soft start components are on the NEUTRAL line and comprise R22, PTC1, PTC2 and the contacts of RLY1. At switch on, R22 limits surge current and PTC1, PTC2 protect R22 from overheating. After a few seconds, the protection circuit energizes RLY1 coil, closing RLY1 contacts which short out R22, PTC1, PTC2, allowing full power operation.
The amplifier should be muted until RLY1 pulls in.
It won't work with the 100W bulb in circuit as there won't be enough current available when required at power up.
Why did you replace the speaker relay and which transistor did you replace?
I found on my 1300 W Peavey that I had to use a 1200 W room heater element instead of a 100 W bulb to limit the current to prevent damage. This made clinking noises when it was protecting when the outputs were at rail voltage, instead of lighting up. It prevented explosions of the stressed output transistors, however, as happened without a limiter.
If the soft start won't work that way, another possibiity is putting the room heater element or other high power resistors in series with the output of the rail supply. These voltages are connected usually with 1/4" flag terminals in high power amps, so making a wire harness just involves wire, some terminals from dorman (auto supply parts) and a good crimp tool. My room heater element had male 1/4 flag terminals already.
If the soft start won't work that way, another possibiity is putting the room heater element or other high power resistors in series with the output of the rail supply. These voltages are connected usually with 1/4" flag terminals in high power amps, so making a wire harness just involves wire, some terminals from dorman (auto supply parts) and a good crimp tool. My room heater element had male 1/4 flag terminals already.
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Q17B MJ15025 was replaced both times.
Speaker relay burned in same channel, due to the excessive current when Q17B shorted to rail voltage i think. Speaker is still ok though...
Speaker relay burned in same channel, due to the excessive current when Q17B shorted to rail voltage i think. Speaker is still ok though...
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