this GK amp is all back together and running great. I replaced the power filter caps and corrected wiring mistakes made by someone? They did not quite figure out how to wire the 2 B+ leads off the pwr transformer to produce a positive and negative power rail. Thank goodness they didn't blow any components.  Jack D

The amp head I have is labeled GT2000 but there are lots of similarities. The amp does have a switch to change the output from 4 to 8 ohms so the output transformer is the answer I am sure. Thanks a million gents!

I received a GK Gt2000 to try and repair. I have not been able so far to find a schematic for it. It uses two pcbs: 50015C pwr amp, and 50016A preamp. Everything on this amp is pretty straight forward except it uses 2 large transformers; One is obviously the power supply and it tests good. The 2nd one is on the other end of the chassis and 2 of it's secondaries go to the 2 pwr transistors (collector?). I am not sure what I am suppose to see coming off the secondaries. Someone has re-wired things inside and they had the positive lead to this 2nd transformer coming off the + pin of the bridge rectifier which is obviously DC volts going in the 2nd trans. Any help would be appreciated.

Jack D

Just a comment about finding suitable replacement PTs. I have had a string of amps on my bench lately that had Pt problems and needed to be replaced. Do to the high, and going higher, cost of new transformers and my skepticism about important parts that say 'made in china' I was on the lookout for a sensible solution. I sort of stumbled onto a supply of low cost PTs when I bought a couple used, powered sub woofers at local re-sale shops. Almost always what is commonly referred to as the 'plate' amp, is non-functioning. But about 80 percent of the time the power transformer is still good. So, even though most of the sub woofer is basically junk, for the grand sum of around 5-10 dollars I end up with a tried and tested power transformer to use for other repairs. One note; buying the bigger, name brand subs is the only way to be fairly confident that the PT will be powerful and strong enough to substitute in amps like a 50 watt Laney SS amp. Here are some names of sub woofers that use better parts and are rated at higher watts: Boston Acoustics, Bose, Klipsch, JBL, Acoustic Research, BandW, Denon and Polk Audio just to name a few.

I will gladly pull the chassis and takes some pics. No problem. Thanks for your input.

I have not been able to find a schematic for this one anywhere. I'll pull the chassis again and try to draw it.
thanks

I have a 1979 Premier P50R ss amp and I would like to put a fx loop between the preamp and the power amp. Does anyone have a good, working example / schematic they could post?  Here's a picture of the little amp. It only makes about 10 watts so I would like the option of bypassing the preamp and seeing what kind of power and tones I can find using other pedal type preamps. Thanks 

good idea. If you have a good quiet 9 volt wart there are several inexpensive DIY pcbs on the market that use an IC chip to make higher voltages. General Guitar Gadgets has one that makes 3 different voltages. Be mindful that these voltage gadgets are not generally used for 'amps' they are used for pedals. So, the current draw of your Supro style amp may be much higher than what these devices can handle. Here is a link.

http://www.generalguitargadgets.com/effects-projects/power-supplies/charge-pumps/

Here is another link with lots of verified builds and if you scroll down to the section called "Misc."  there are 3 different power source projects with good info.

http://diy-fever.com/

I have a Boss 9 vdc pedal wart that is not too noisy. However if you are digging thru the wart box at the local resale shop looking for one that claims 18 vdc output, 99 times out of a hundred it will be too noisy. If our friend wants to run 18 volts then finding a quiet one would be difficult in my opinion. It doesn't cost much to try so have a go at it.

hello noob from Aussie land. What are you building the amp for? A guitar, a PA system, a headphone amp? My experience with warts is they always make a lot of noise thru the circuit. Sometimes so much noise that they are unusable for audio/music applications. If you describe what you are wanting the amp to do, maybe we'll have some more ideas about which project and or power supply method to use.

JD

I purchased a Peavey Renown 400 that was not working. I worked with that amp a long time without success trying to make it work as it came out of the factory (I am a novice at SS repairs). The preamp section worked fine so I mounted it in a box and have experimented with several types of power amps using a jumper cable from the "preamp out" jack.

How many AC volts does the PT put out on the 2 mains? How many DC volts do you get at the rectifier and large filter capacitors?

I guess he meant some other kind of "interest" other than people responding to his post?

you should be able to date this amp with the numbers/letter code on the power transformer and also stamped on the back of the pots. One of the numbers (don't recall exactly which but sometimes the first number right of the dash mark -) will give you the last number of the year. You have to use other methods e.g. material of corners to figure out which decade. example  A35-6973 would be either 1976 or '86 or 96' or '06 and use other indicators to decide which of these decades. If you can read the speaker numbers they can also tell the date of mfg. of the speakers which is usually within a yr or two of the mfg. date of the amp.

just FYI; getting the spkr watts rating equal to your amp's output is not the key to making your rig sound great. I would not hesitate to use spkrs rated at 60 watts with a 100 watt peak amp. BUT, the tonal qualities of the spkr itself and, in small part, the design and building materials used for the cab, will determine if it produces the "sound" you are looking for. Again, trying dozens of different combinations will be very costly so get some recommendations and try a couple different spkrs in a good cabinet (the best cabs in the sixties i.e. Blackface Fender cabs, were all made with seasoned Pine and voidless ply sound board with an open back). The best cabs available today are all made with voidless plywood, NOT pressbrd or sawdust board. Most cabs for lead guitar are open back. Most cabs for bass are closed back. There are some good cabinet builders out there but they're not inexpensive so be sure what you want before you buy. I see lots of good 'looking' unfinished pine and ply cabs for sale on ebay but I know nothing about any of those sellers.

Remember that the BIGGEST issue is the type and quality of the spkr itself, so that's where you want concentrate your most time and money to get the BEST result.

smacko jack    :tu:

there could be numerous combinations of cabinets and speakers that sound good with your amp. the biggest problem is trying to 'test' different brands and models without having to buy dozens. gets real expensive real quick. I prefer the blue label Fender 12s for blues and vintage rock sound. I don't think you can go wrong with either EV or JBL high end speakers. I don't think they sound as good as some of the ones with smaller magnets though except when pushed really hard by some mega watts. Case in point would be the late, great Jerry
Garcia.

Here is a link to a picture of the blue label Fender speakers. They are plentiful, priced right and can handle a lot of guitar sound.

http://www.ebay.com/itm/Vintage-Fender-Twin-Reverb-The-Twin-Red-Knob-Guitar-Amp-Combo-Amplifier-LL66385-/251538046908?pt=LH_DefaultDomain_0&hash=item3a90d5ffbc