| Need Help with Frankie head [message #13738] |
Sun, 23 May 2010 19:02  |
BrianBB
Messages: 46
Registered: November 2008
Location: Fayetteville, Ga.
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Hi everyone,
I last visited here about 6 months ago when I needed advice on buying a charcoal Frankenstein bass rig. The amp sounds great but has a loud hiss in the right channel when the treble is turned up. It happens with or without a guitar plugged in and makes the channel unusable for recording or playing out anywhere but a noisy bar. Any ideas to the cause and how to fix it?
Thanks.
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| Re: Need Help with Frankie head [message #13748 is a reply to message #13738] |
Mon, 24 May 2010 11:44  |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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The hiss that you describe is fairly common on the Frank heads. Some are better than others, some are worse. Apparently you have one better and one worse channel.
The treble control in the Frank preamp circuit does 2 things. One, it changes the amount of high frequencies that are boosted or cut and two, it increases the high frequency response of the input stage. That being said, there will always be some hiss in the circuit with the treble control set to maximum.
To try and reduce the hiss, you can try replacing the first 3 transistors in the bad channel, try replacing the related resistors in the front end of the channel and also try changing the electrolytic coupling caps in the channel.
If it was mine, I'd start by replacing the coupling caps as they are 40 years old and probably need replacement anyway. Whenever I do this to a preamp, I find that there is a great improvement in the overall frequency response of the amp.
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| Re: Need Help with Frankie head [message #13751 is a reply to message #13738] |
Mon, 24 May 2010 14:57 |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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If you follow the shielded cable from the volume control to the pc board it will lead you to the input cap of the preamp, which on a Frank head is in the middle of the board. There are three transistors in a row starting from the input cap and heading to the right side of the board. These are the first three that you are looking for.
That being said, I'd still suggest that you replace the caps first.
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| Re: Need Help with Frankie head [message #13754 is a reply to message #13738] |
Mon, 24 May 2010 18:10 |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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My 2 cents.
Each model of the Kustom heads is slightly different in design and so there are subtle sound differences and major feature differences.
The Frank heads have a power amp design that uses a driver transformer, so it will distort differently from the other series heads. Some say they are a bit more tube like in the break up. The power amp is similar to the ones used by Thomas Organ Vox amps as well as early Acoustic Control amps.
The A-Series heads started the use of the transformerless output amp. These amps are a bit louder, cleaner than the Franks and also introduced the use of multiple FX to the line.
The B-Series improved the preamp design for the line, but for some reason they decided to split the FX to the two channels instead of having all of the FX on one side.
The 150-250 Metal fronts added a new preamp design using ICs and have the FX on both channels. These also increased the power output slightly and added the ability to blend trem and vibrato together again.
Which one is best depends upon what you want the amp to do. If clean sound is important, almost any of the heads will do clean really well. If FX are important then try them all and see if one set of FX work best for your sound. A lot of the guys here say that they use outboard FX in front of their amps with no problems.
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| Re: Need Help with Frankie head [message #13758 is a reply to message #13738] |
Tue, 25 May 2010 06:09 |
stevem
Messages: 4788
Registered: June 2004
Location: NY
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Senior Member |
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Kustom never made a bass amp in a strick sence untill the middle to late 70s when they where owned by Baldwin organ company.
What most people concider and as Kustom intended, a bass head was just a Frank, A serise or B serise head without effects.
I find the Frank heads to be the warmest sounding heads with the early 100s a close second, but the Frank heads can sound harsh.
Frank heads use a ton of coupling and bypass caps on the circuit boards and these componets drift in valve massively as the amp ages, in fact more so if the amp goes unused for long periods of time.
This drifting in value can make for greatly increased gain and noise in certain frequncey ranges that can make for the harshness you dislike.
Replacing 25 dollars work of 40 year old caps can make for a huge difference in tone and placing the amp back to the way it sounded when new.
It would also be a very simple thing to and a cap and resistor network to just one input of the amp to roll off some of that spiky high end that you do not like.
[Updated on: Tue, 25 May 2010 06:10] Report message to a moderator |
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| Re: Need Help with Frankie head [message #13763 is a reply to message #13762] |
Tue, 25 May 2010 11:24 |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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BrianBB wrote on Tue, 25 May 2010 09:39I guess it would help to have a picture of the chassis and which parts needed to be changed rather than a schematic. I can read schematics but prefer a layout of the circuit. With a picture of diagram I'm sure I could work on it myself.
Kustom didn't create pictorial layouts for these amps. They did for the later series. There really aren't that many parts in these circuits, you should have no trouble if you have basic soldering skills. Do you have the schematic? By the way, which model do you have?
BrianBB wrote on Tue, 25 May 2010 09:39Are there any comprehensive books on vintage Kustom amps, like there with Vox, Fender, Marshall?
Not that I know of. Maybe some of the guys here can talk to Bud Ross about writing one.
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| Re: Need Help with Frankie head [message #13771 is a reply to message #13738] |
Tue, 25 May 2010 22:20 |
BrianBB
Messages: 46
Registered: November 2008
Location: Fayetteville, Ga.
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Pleat,
Sign me up for the first copy of the book. I would love to see one.
Here are my three Kustoms, all are plexi faceplates:
My )))K200((( has two channels with volume, bass, treble, and bright switch, high and low inputs on each, plus a blue jewel light. it has no plate on the back. Power switch on front middle.
The )))K100((( has one channel and high and low inputs with vol., treble, bass, reverb, speed, intensity. Plate on back says K100 2. Red pilot light. Power switch in back.
The Frank has the same two channel layout as the K200 without the bright switches. Back plate says C 595 CHARCOAL. Red pilot light. Power switch on front right side.
Are these A or B series? Did they really make them without power transformers?
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| Re: Need Help with Frankie head [message #13776 is a reply to message #13738] |
Wed, 26 May 2010 06:06 |
stevem
Messages: 4788
Registered: June 2004
Location: NY
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Senior Member |
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Brian you kind of anwsered your own question.
Your K100 is a k100-2 model like you posted, and this is just a head, one of only three K100 heads in the kustom line up that they ever had . These models first came out in 68.
Your K200 amp would be a A serise model if it has a white circuit breaker button on each side of the on/off switch, other wise its a latter B model when they ditched the breakers and went to internal fuses.
Your Frank head is the standard model used for both bass and guitar.
All kustoms have power transfomers, and as in all solid state amps that are not made for 70 volt paging system use, they have no output transfomer also.
The Frank heads do use a output stage driver transformer which is quite unusual for a solid state amp, and I would love to know why Bud choose to go that route.May be they still did not trust the transistors they had to pick from for driver use at that point in time and fell back on something that could be counted on 100%.
[Updated on: Wed, 26 May 2010 06:08] Report message to a moderator |
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| Re: Need Help with Frankie head [message #13782 is a reply to message #13738] |
Wed, 26 May 2010 11:40 |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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Pleat: Great to hear about your book. Will it contain history of Bud and the company as well as nuts and bolts?
All of the Frank heads were called K200 Energizers. There were three versions:
1-Basic Model 96000 2-Channels, High/Low Inputs, w/No FX.
2-RV Model 96001 2-Channels, High/Low Inputs, w/Reverb and Vibrato on left channel.
3-PA Model 96002 2-Channels, w/Reverb on left channel.
All three models had the Speaker and Power fuses on the right front panel under a three way power switch. And most came with red non-jeweled pilot lamps.
Stamped on the Serial number sticker plate was the Model Number which was usually a coded number and letter combination that described the features and the list price of the amp/speaker combination.
So L795 meant that the amp originally came with Lansing speakers and cost $795.00.
C595 meant CTS speakers and a list price of $595.00.
If the amp had FX or was a PA (Public Address) model there would be an added suffix to the model of either RV or PA, something like L1295RV.
[Updated on: Wed, 26 May 2010 11:43] Report message to a moderator |
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| Re: Need Help with Frankie head [message #13784 is a reply to message #13738] |
Wed, 26 May 2010 12:04 |
chicagobill
Messages: 2010
Registered: April 2003
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Senior Member |
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Remember that during the past 40 years the speakers could have been changed out and that the speaker cabinet that you got with the amp head could have originally been from an different amp.
I suppose that even the original dealers could have swapped speaker cabs to fulfill the specific needs/wants of a customer.
Beginning with the plex front K200A's all of the fuses were moved inside the head. The speaker fuse was eliminated in the B series.
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