Somebody should call NASA.  It looks like one of their satellites is missing.

Quote from: joecool85 on May 16, 2011, 11:03:48 AM
...Where can I get a $99 USD 5w tube amp?  I'll go get one today just for giggles.

Musicians Friend has these on sale now...

http://guitars.musiciansfriend.com/product/Kustom-Defender-5H-Guitar-Amp-Head?sku=423624

Kustom Defender 5H Guitar Amp Head Features:

Volume control
1/4" input
Power button
One 12AX7 preamp tube
One EL84 power tube
Three speaker outputs (4, 8, and 16 Ohm)
One knob does so much on this 5W head. Order now and get tube sound for a killer price.

Maybe these 7Watts from mouser, wirewound, 22.2 mm length?:

66-W22R270JRLF

66-W22R470JRLF

You might find a niche by highlighting the durability/well-built nature of your 5W amp over the competition.  The small cheap amps seem to suffer from simple mechanical damage.   Your build quality versus thin pcbs, flimsy jacks, thin chassis material, etc.

Does Weber Speakers publish SPL figures?  Your question prompted me to look and I didn't see any.  I have used their alnico and ceramic 8" signature 8S speakers in champ-type circuits and liked them, but don't know specs.  They are low watt, about 15W, however.

Quote from: teemuk on May 10, 2011, 01:29:16 PM...I think TDA2020 + TL70x is a kinda broad description but it practically describes a lot of what's already in the markets...

I was going to say, the concept sounds kind of like my Crate GTX-15 with a better speaker.

Quote from: teemuk on May 05, 2011, 01:13:43 PMI think one good distinction between the versions should be that the "set B" has a "rock-n-roll" switch ...

Wow!  A "Rock-n-roll" switch.  Now if I could just find and amp with a "Play Better!" switch.

Quote from: kernalflagg on April 25, 2011, 02:22:01 AM
I managed to get a couple of close-up pics of some ballast resistors from an RG100es.

I have a few questions:

1) Do you know if the ones in your amp were made by Colber?
2) Do they look like these?

The ones in mine look exactly like the brown one on the top of your picture.  They do not say "Colber" on them.

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMIn your amp, does all 4 look like the sam type and construction as those in the pic from the link you posted?

Yes.  They are rectangular, axial.  The orginal ones are brown, The mouser xicon ones are white, but that isn't a concern.

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMI doubt they would be vertical mount, but just to make sure, they are axial right ?

Yes, you want the axial ones, they lie flat on the board.

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMThe only thing that bothered me was that I couldn't find any 7W ones listed on the spec sheet. I wonder if it makes a difference to go with 10W or not. I know that they had a lower heat dissapation temp, but I'm not sure how that would affect it, if it will at all.

As to the wattage, 10w rating will be okay versus 7W original.  As to heat dissapation temp, I didn't see that spec, but 10 watt rated device should dissipate more power than 7W, so should not cause a problem.

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMI found some made by Ohmite (PN# TUW7) that listed both the 0.6ohm/7w and 0.27ohm/7w but I'm not sure if any of these are right type and construction. They don't give an actual photo of any of them, just a drawing.

These should also work.  Your big concerns are resistance, power rating, will it fit and can you find a supplier that has it.  You have your board and hole spacing so you can measure before you buy and tell if it's too long or wide or not.

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMAlso for the TUW7, they give a "range" of values (0.1 to 680) for ohms, instead of specific values. I wonder if that means you can order any value that is in the range?

Yes, the description you linked to is giving the range of values.  You have to check if you can source the specific standard value (.27 or .6) you need from your vendor. I looked at mouser and digikey but I didn't see the TUW series in values you need and in-stock.  They had the 15w, but that is pretty chunky size: 12.5 mm W x 49 mm L x 11.5 mm H

http://www.mouser.com/Passive-Components/Resistors/Wirewound-Resistors/Wirewound-Resistors-Through-Hole/_/N-7fx9i?P=1z0x6u4&Keyword=ohmite+TUW&FS=True

Quote from: kernalflagg on April 18, 2011, 11:23:04 PMI'm also wondering if I need to be concerned that thye are rated at 500V?

How much voltage does the circuit have on that part?  The whole power supply is only about 82 volts in mine.  Those parts are probably around 41 volts, n'est-ce pas?

In my RG80/112SC these resistors are just rectangular, wire-wound .6 / .27 Ohm 10% 7-Watt.

I think mouser will have 7 or 10 watt replacements with similar dimensions:  Maybe have a look at this PN at mouser280-CR10-0.27-RC ?

http://www.mouser.com/ProductDetail/Xicon/280-CR10-027-RC/?qs=gI4ZKBuUnui5tgBooyyNvg%3d%3d

I have an RG80 that has a bit of power-amp hum (I talked about it on another board).  After fiddling with it (I still have bit more fiddling I plan to do) I am maybe coming to the same conclusion about accepting some hum.

Sure thing.  Please share!

The op amp on the pc board is for the reverb send and return circuit.  It happens to be 4558 on the schematic, but in my post I was referring to a pedal that I particularly like, which concidentally also uses the same chip.  Regarding, changing the op amp, I have done that.  When I got my amp it had a socket for the chip already installed.  I don't know if Randall did that or someone else, but a previous owner or experimenter had mis-installed the op amp upside down.  When I got the amp the owner (he said it was his brother's amp) told me the reverb didn't work, and really it was just the chip inserted wrong, I flipped it over and it worked.  Anyhow, the chip in my amp (the upside down one) when I got it was a 5332.  I also tried a 4558, which worked fine.  It may be the 5332 was a little quiter, less noisy, but I wondered if it wouldn't pull a little more current, so I left the 4558 in there.  I didn't notice a big difference in the reverb, to be honest.

The program is asking for the source impedance of the preceding stage and the input impedance or load for the next stage.  I think the default value on the Marshall tone stack in the program is for a tube stage (1.3K). I'm not the most savvy on this stuff, so I am hoping one of the gurus will weigh in, but if your randall schematic is the same as my the RG 80, there is a 10k resistor, a 10K pot and a 1MFd cap coming from the preceding stage.  I know cap impedance varies with frequencies, but should be smaller, relative to the resistors (maybe 1,500 to 150 ohms at guitar frequencies?).   On the next stage there is a 1M resistor in front of the driver transistor and 1M in front of the op-amp going to the reverb, so maybe 500K in parallel?  Also the schematic indicates the ac voltage at 1Khz before and after each stage, so someone who is good with the math can probably deduce the relative values of input and output impedance.  I was playing aorund in the program with 10k-20k on the source and 1M and 500k on the load.  It looks like the chief effect is to move the whole curve up or down (like adding or subtracting a constant).

Quote from: J M Fahey on March 30, 2011, 11:22:37 PM.
Well, it probably was made on purpose.

I suspected as much.  Once I figured out that they were like this it was easy to deal with but I did feel stupid at first pulling on the loose cap and it not coming out of the board.