Hiwatt g100 resistor values

[philly]

Hi all,
I am repairing a Hiwatt g100 112r transistor amp for a friend and have found 2 transistors faulty. Also blown are resistors r15 and r16. As these resistors are badly burned I cannot read the colour code values. Anyone have a schematic that could check the values for me please.
Thanks in advance.

[Jazz P Bass]

This is all that is on the site: hiwattmaxwattg50r40r.pdf

Maybe try contacting them:

Hiwatt Maxwatt Guitar Amps

[J M Fahey]

Absolute worst case, you can draw the output stage schematic, mainly the power transistors and their drivers and the resistors directly connected to them, among which must be R15/16 .

Suspect they might be the Base to Emitter resistors in the power transistors, chech what are they connected to.

IF so, we can suggest reasonable values.

In any case build a lamp bulb limiter and use it, to avoid burning other parts you have not yet detected.

Alsopost a picture of such resistors, at least to have a clue on wattage/dissipation/size.

[philly]

Absolute worst case, you can draw the output stage schematic, mainly the power transistors and their drivers and the resistors directly connected to them, among which must be R15/16 .

Suspect they might be the Base to Emitter resistors in the power transistors, chech what are they connected to.

IF so, we can suggest reasonable values.

In any case build a lamp bulb limiter and use it, to avoid burning other parts you have not yet detected.

Alsopost a picture of such resistors, at least to have a clue on wattage/dissipation/size.

Thanks bud,
The faulty transistors and resistors are not at the final o/p stage but are I think two steps back. The resistors are 1/4 watt and the transistors in question are low power Q7, Q9 which are A970 and C2240.

[philly]

This is all that is on the site: [ATTACH]41528[/ATTACH]

Maybe try contacting them:

Hiwatt Maxwatt Guitar Amps

Thanks bud,
I have seen this schematic before and it is not the same as mine.
Thanks for your feed back.

[musictronics]

R15 & R16 are both 47R, emitter resistors for Q7 & Q9 respectively

[musictronics]

R15 & R16 are both 47R, emitter resistors for Q7 & Q9 respectively

Actually... in latest version they're changed to 330R each - just noticed that!
Other changes to this version: R20 & R23 are now 12K (were 100R) and there is a Cap (C700 0.22uF/63V) added between collectors of Q7 & Q9.
I hope this helps.

[philly]

Actually... in latest version they're changed to 330R each - just noticed that!
Other changes to this version: R20 & R23 are now 12K (were 100R) and there is a Cap (C700 0.22uF/63V) added between collectors of Q7 & Q9.
I hope this helps.

Thanks bud,
This is progress as I tried calling Hiwatt UK earlier and it seems as the line in no longer in service. I will go with your information and fit 47 ohm as the emitter resistors on Q7,Q9. R20 & 23 are 3.5k on my board so it looks as if there has been many mods to this model.
Thanks again for your help. Keep you all posted.

[J M Fahey]

R15 & R16 are both 47R, emitter resistors for Q7 & Q9 respectively

You seem to have the schematic available, can you please post it here?
Thanks

[philly]

You seem to have the schematic available, can you please post it here?
Thanks

Hi JM Fahey,
I don't have a schematic at all. Musictronics has been helping me with the resistor values as you can see in yesterdays posts.
Jazz p Bass posted this,
http://music-electronics-forum.com/a...attg50r40r.pdf

[philly]

Update.

Thanks bud,
This is progress as I tried calling Hiwatt UK earlier and it seems as the line in no longer in service. I will go with your information and fit 47 ohm as the emitter resistors on Q7,Q9. R20 & 23 are 3.5k on my board so it looks as if there has been many mods to this model.
Thanks again for your help. Keep you all posted.

Received transistors from Futurlec.com (which I highly recommend, great prices and availability) and replaced Q7, Q9, R 15 & R16 and all seems to work fine. I played a guitar through it for 15 mins and no sign of smoke. I did observe that Q7 is running hot even with no signal input. Maybe this is normal. I haven't measured current through Q7 or voltages yet. I also replaced resistors R10,11 & 13 (1.5k) as these looked like they suffered overheating at some stage in the past. The owner mentioned that condensation / moisture may have caused the original problem as the unit lives in the van during gigs.
Any comments welcome.

[philly]

schematic hiwatt

You seem to have the schematic available, can you please post it here?
Thanks

Found this today.
Same as my G100 112R
RandallRG75BPowerAmpsketch_zps6fa10afc.gif gif by dobz3 | Photobucket

[philly]

Received transistors from Futurlec.com (which I highly recommend, great prices and availability) and replaced Q7, Q9, R 15 & R16 and all seems to work fine. I played a guitar through it for 15 mins and no sign of smoke. I did observe that Q7 is running hot even with no signal input. Maybe this is normal. I haven't measured current through Q7 or voltages yet. I also replaced resistors R10,11 & 13 (1.5k) as these looked like they suffered overheating at some stage in the past. The owner mentioned that condensation / moisture may have caused the original problem as the unit lives in the van during gigs.
Any comments welcome.

Went by older post and changed resistore to 330 ohm. Trannys now run cool.
All seems ok.
Thamks to all for your help.