Hammond Service

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DIY Service

General information

Tech Talk

Hard-to-find info, schematics


Was Sie selbst tun können (deutsch)


Was die Werkstatt für Sie tun kann (deutsch)

General DIY Service Suggestions for T-Series Organs and Others

If you understand german, read also here: Was Sie selbst tun können. Or, if not, see also the HammondWiki Topic Repair. However, the Wiki is more or less dedicated to console organs. 

Tone missing, too loud or too soft

Locate the offending tone number by consulting the manual wiring chart. Example: The first C# on 16' rank is missing on upper manual. The manual wiring chart translates the first C# on sub-fundamental to tone numer 26. Locate the magnet location of tone 26 and tone 26 on solder terminal strip. Hook up a AC Millivoltmeter to this tone output. Check the coil for proper grounding and intact wiring.

Often the coil is intact, but has a bad ground connection due to a rusted rod. Try grounding it's pins by a short wire. Resoldering the coil's solder joints may also help.

Too loud or too soft tones may be adjusted as described in the generator recalibration procedure.

On later console organs, Gooey Foam (also referred as "black foam", decomposed foam plastic used to secure wires) often oxidizes the resistor wires in the manual contact compartment. It had to be removed completely in a workshop, otherwise things get worse.

Generator won't turn

If your Hammond has been stored for a long time, the generator may be stuck or "frozen". Remove the fiberglass mat from underneath the generator and give it a WD-40 shot on ALL bearings. Do not forget the motor and scanner. Fill in two thimblefuls of a half-and-half oil/lighter fluid mixture into the generator funnels. This is for breaking up the gummed oil in the cotton threads, especially in the long ones going to the scanner assembly. Wait at least two days to let the WD-40 soak all bearings. Then try to turn main shaft and all wheels by hand. It should turn very easy eventually. Start the Hammond and lubricate with Hammond Oil, about a thimbleful on each funnel. Don't forget the motor's small funnels or the little tub on older Start/Run-Hammonds. The felt in the tub should be wet with oil, not more!

No Vibrato

Check if  the scanner turns. Easy on T-500 -- sometimes the O-ring belt from run motor to scanner (brown can near run motor) is teared off. Replace with thin O-ring from your favorite automotive shop. Otherwise, disassemble scanner and check if it turns easily. Lubricate all gears and bearings.

On older organs, the scanner (flat metal can) is located on the start motor side. Generator has to be removed from organ (at least partly) to disassemle. Often the scanner is frozen due to insufficient lubrication or gummed oil, while the generator still runs. Avoid running the generator with a frozen scanner, otherwise the slip clutch between scanner and generator axle may be damaged. Instructions how to rebuld a scanner can be found at HammondWiki.

Mechanical noise

When the generator or run motor itself is noisy, bad luck. Maybe is has run dry some time ago and some of the bearings are bad. Try a somewhat "thicker" oil (high quality machine oil) as a generator lube, as some car dealers do on V8's with noisy valve lifters. Please note: Using thicker generator oil may lead to start problems on older organs with start/run-motors, especially on cold days. Sometimes the scanner (brown can near run motor on T-500 organs, flat can otherwise) is noisy and has to be disassembled and lubricated (very few drops - or a lithium based "white" grease). Remove drive belt on T-500 or H-Series organs to determine if noise comes from scanner.

Scratchy Drawbars

HammondWiki's cleaning suggestions apply to console organs whith metal-case drawbars only! Avoid spraying the H- or T-Series drawbars with DeoxIt or contact spray, since it deteriorates the plastic material. The drawbar box will literally fall into pieces after a few years if you try this with a miracle spray. The plastic drawbars have to be disassembled and cleaned the "old fashioned way" (shown in pictures 1 2 3 4 5 6), then lubricate with "white" lithium based grease (automotive shop) or vaseline.

Amplifier hums on T-100, T-200, T-500

Replace the tall C603 and C606 electrolytics on main amp pcb. These are 80uF/25V. Use 220uF/35V for C603 and 100uF/35V for C606 as 80uF is no standard value, and more capacity is better in this case. These caps are suspect to dry out due to heat from nearby power resistors. That should help in most cases, although sometimes the big electrolytic cans in the power supply may be weak also.

Amplifier noisy on T-100, T-200, T-500

The transitors used in early T- and H-Series organs are pretty noisy. Replace small signal NPN transistors in all low-signal amplifier stages with BC549B or alike and PNP types with BC559B. Note different case and pinout. Most of the noise comes from the recovery preamp board (5 transistors) and the first main amp/reverb stages (Q601, Q611 and Q612). Changing these will not affect the sound in any way, besides the noise.

Main amp blows fuses on T-100, T-200, T-500

The Hammond power transistors mounted on the heat sink between bass pedals and volume pedal are PNP germanium types. Replace with AD130, AD133 or similar. Check for bias current below 50 mA.

Generator Capacitor Replacement

On all T-, E- and H-Series, this is absolutely not necessary since the dark reddish-brown mylar caps are very stable, even over 40 years. If recommended for any 1965 or later organ, this is a pure rip-off. Anyway, the older wax-paper caps used up to 1964 tend to double or even triple their value over time, which detunes the LC filter bank and causes a muffled sound on the 49 higher notes (higher drawbars). If you prefer a like-new "bite", you should consider replacing the caps, also those on the vibrato line box if vibrato sounds too "choppy". A generator recalibration is highly recommended after replacement. If you do this as a professional service, you should consider my Recalibration Software (runs on Windows PCs with sound/microphone input). Please email me for pricing.

Check my schematics for an appropriate circuit drawing. Captain Foldback's Hammond & Leslie Page also is a good source for Hammond/Leslie schematics and service manuals.